JP2007208059A - Micro-lens, manufacturing method thereof, solid imaging element using same, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro-lens wherein the variation of its shapes is reduced and it has a stability, a good reproductivity, and a high condensing efficiency; and to provide a stable, highly sensible, and highly reliable solid photographing element. <P>SOLUTION: The micro-lens has a plurality of lens surfaces provided oppositely to a plurality of respective photoelectric converting regions constituting pixels. Further, the micro-lens has each core body 61 which is so provided grid-wise as to stand in the region interposed between respective lenses correspondingly to the forming pitch of the lens surfaces of the micro-lens, each wall 62 having a first refractive index and having concave surfaces so provided as to cover the core body, and each lens 60 having a second refractive index higher than the first refractive index and so provided as to contact with the concave surfaces of the walls and filled into each region surrounded by the walls. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microlens, a manufacturing method thereof, a solid-state imaging device using the microlens, and a manufacturing method thereof, and particularly relates to shape control of the microlens.

  A solid-state imaging device using a CCD used for an area sensor or the like includes a photoelectric conversion unit including a photodiode and a charge transfer unit including a charge transfer electrode for transferring a signal charge from the photoelectric conversion unit. . A plurality of charge transfer electrodes are arranged adjacent to each other on a charge transfer path formed on the semiconductor substrate, and are sequentially driven.

  In recent years, with the miniaturization of cameras, demands for higher resolution and higher sensitivity are increasing in solid-state imaging devices, and the number of imaging pixels is increasing to more than gigapixels.

  In order to improve the sensitivity, various structures have been proposed in which a microlens is provided on the pixel surface to increase the light collection efficiency to the photodiode.

  For example, as shown in FIG. 13, an in-layer lens that also serves as a passivation film is formed on a planarizing layer immediately above the photodiode unit 30 constituting the photoelectric conversion unit, and a planarizing film ( A structure in which a light-transmitting film), a color filter, a planarizing film, and an on-chip lens 60 are sequentially formed has been proposed.

  Conventionally, when a solid-state imaging device using the on-chip lens 60 is manufactured, a microlens pattern made of a transparent thermosoftening resin, which is a microlens base material, is formed on a photoelectric conversion unit using a photolithography technique. Then, heating is performed to reflow the microlens pattern to form a microlens.

  By the way, the area between the lenses becomes an invalid area that does not contribute to photoelectric conversion because light passing therethrough is not guided onto the photodiode. Therefore, as a method for narrowing the lens interval, a method has been proposed in which the lens interval is reduced to 0 by processing the substance into a lens shape with an interval on the planarizing film and expanding the material. (Patent Document 1).

JP-A-6-252372

  However, in the microlens manufacturing process described above, a microlens pattern made of a thermosoftening translucent material is softened by heat, so that the shape of the microlens obtained is the thermal history of the microlens base material. It is determined by the surface state of the planarizing layer, the film thickness, dimensions, etc. of the microlens pattern. Therefore, variations in the shape of the microlens 60 occur as shown in FIG. 14 due to variations in temperature, microlens pattern dimensions, film thickness, etc. during thermal reflow. For example, the temperature is 1, 2 ° C., and the time is in seconds. Even if it changes, it will fluctuate greatly. In addition, since the reproducibility with respect to the thermal history after the microlens formation is low, the height of the lens is likely to fluctuate, and there is a problem that a highly condensing lens cannot be formed with good reproducibility.

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a microlens that reduces the variation in the shape of the microlens and has high light collection efficiency with high reproducibility.
It is another object of the present invention to provide a solid-state imaging device that is stable, highly sensitive, and reliable.

The present invention is a microlens having a plurality of lens surfaces arranged so as to face each of a plurality of photoelectric conversion regions constituting a pixel, each corresponding to the formation pitch of the lens surfaces of the microlens. A core portion provided in a lattice shape so as to stand in an inter-lens region of the lens; a wall portion having a concave surface having a first refractive index provided so as to cover the core portion; and the wall portion And a lens portion having a second refractive index higher than the first refractive index, which is provided so as to be in contact with the concave surface, and is filled in each region surrounded by the wall portion. To do.
By this configuration, a lens portion is formed by forming a wall portion having a concave surface so as to cover the core body portion that has been previously shaped and filling the concave surface with a high refractive index material. It is possible to provide a microlens having a reduced and stable and constant shape. In addition, a film that covers the core part is formed on the surface of the core without undergoing a melting step, and a curved surface is formed by utilizing the surface tension of the film or wettability with the core part. Therefore, variation in height can be reduced, and highly accurate shape processing can be performed.

The present invention includes the above microlens in which the wall portion is formed of a coating film.
With this configuration, a coating film that covers the core body portion is formed on the surface of the core body, and a curved surface is formed using the surface tension of the coating film or the wettability with the core body portion. Variations in thickness can be reduced, and highly accurate shape processing is possible. The thickness of the lens can be controlled mainly by the height of the core portion, and the curvature of the lens can be independently controlled by the viscosity of the coating film constituting the wall portion.

In the microlens according to the present invention, the core body includes a first resin.
With this configuration, a desired shape can be easily obtained by coating.

In the microlens according to the present invention, the core includes an inorganic film.
With this configuration, it is possible to form a wall portion having high mechanical strength and strong against changes with time.

The present invention includes the above microlens in which the wall portion is made of a second resin.
With this configuration, since the wall portion is composed of the second resin formed so as to cover the core made of the first resin, the shape can be easily controlled by application without passing through the melting step. According to this configuration, the controllability is greatly improved because it is only necessary to control the round shape of the wall with the surface tension of the resin covering the core body, as compared with the conventional microlens that obtains the lens shape itself by melting. improves.

According to the present invention, in the microlens, the wall portion includes an inorganic film.
With this configuration, it is possible to provide a microlens having high mechanical strength and high reliability. In this case, since the wall is formed by applying an inorganic film such as an SOG film so as to cover the core after forming the core, the wall is formed with good controllability and reproducibility. It becomes possible to do.

According to the present invention, in the above microlens, the lens portion includes a third resin.
With this configuration, since the lens portion can be formed simply by filling the wall portion with the third resin, it is possible to easily form the lens portion having desired optical characteristics.

According to the present invention, in the microlens, the lens portion includes an inorganic film.
With this configuration, the mechanical strength can be improved. In particular, the mechanical strength is greatly improved by forming the wall portion with an inorganic film and the lens portion with an inorganic film.

The present invention includes the microlens in which the wall portion is formed of a silicon oxide film that covers a core, and the lens portion is formed of a silicon nitride film.
With this configuration, the optical characteristics and mechanical strength are improved, and the element portion is covered with a two-layer film of a silicon oxide film and a silicon nitride film, so that the insulation and moisture resistance can be improved. Can do.

The present invention includes the above-described microlens composed of a high refractive index inorganic polymer. The wall includes a SOG film, and the lens includes a high refractive index inorganic polymer.
With this configuration, it is possible to improve mechanical strength and moisture resistance. Examples of the high refractive index inorganic polymer include high refractive index inorganic polymers to which zinc oxide, titanium oxide, tin oxide or the like is added.

The present invention includes the above microlens in which a difference in refractive index between the wall portion and the lens portion is 0.4 or more.
With this configuration, the light collecting characteristics can be further improved.

The present invention includes the above microlens in which the core body portion has a refractive index smaller than that of the wall portion.
With this configuration, the light incident on the wall portion is totally reflected by the core body portion, whereby the light incident on the solid-state imaging device can be more efficiently photoelectrically converted. In addition, since light that escapes to adjacent pixels is suppressed, color mixing can be prevented. In addition, you may form a core part with a light-shielding member.

The present invention includes the above microlens in which a cross-sectional shape of the core body portion is a forward tapered shape.
With this configuration, even if the critical angle of total reflection determined by the ratio of the refractive indexes of the core and the wall is the same, the incident angle of incident light that can be totally reflected can be widened, and high sensitivity can be achieved. . Moreover, since the area | region which cannot inject into the photodiode immediately above a core part reduces, high sensitivity can be achieved.

The present invention is a method of manufacturing a microlens that is arranged to face each of a plurality of photoelectric conversion regions constituting a pixel and includes a plurality of lens surfaces, and corresponds to the formation pitch of the lens surfaces of the microlenses. And forming a lattice-shaped core body portion having a first refractive index so as to stand in an inter-lens region of each lens, and covering the core body portion, having a first refractive index, Forming a wall portion having a concave surface curved with a desired curvature, and filling the wall portion with a member having a second refractive index to form a lens portion.
With this configuration, since the wall portion having a concave surface curved with a desired curvature is formed by a method such as forming a coating film so as to cover the core portion, it can be formed without using a melting method. It is possible to shape the wall portion with good controllability, reduce variation, and form a highly accurate and reliable microlens with high reproducibility.

The present invention provides the microlens manufacturing method, wherein, prior to the step of forming the lens portion, etching is performed under an etching condition such that etching rates of the core body, the wall portion, and the base layer are equal, and the wall A step of transferring the shape of the portion to the base layer to form a wall portion made of the base layer.
With this configuration, it is possible to further improve the mechanical strength as compared with the above method.

According to the present invention, in the method for manufacturing a microlens, the step of forming the lens portion includes a step of flattening the surface.
With this configuration, since the surface is flat, it can be applied as an in-layer lens.

A solid-state imaging device according to the present invention includes a photoelectric conversion unit including a plurality of photoelectric conversion regions constituting pixels, a charge transfer unit including a charge transfer electrode that transfers charges generated in the photoelectric conversion unit, and The microlens is mounted on the surface of the substrate on which the peripheral circuit portion including the wiring layer connected to the charge transfer portion is formed.
With this configuration, a microlens having a stable and constant shape is mounted, and it is possible to suppress characteristic variation and provide a highly reliable solid-state imaging device.

The present invention provides a photoelectric conversion unit including a plurality of photoelectric conversion regions constituting a pixel, a charge transfer unit including a charge transfer electrode that transfers charges generated in the photoelectric conversion unit, and the charge transfer unit. On the surface of the substrate on which the peripheral circuit portion including the wiring layer to be connected is formed, a lattice-shaped core body portion is provided so as to stand up in the inter-lens region of each lens corresponding to the formation pitch of the lens surface of the microlens A step of forming, a step of forming a wall portion having a concave surface that covers the core portion, has a first refractive index, and is curved with a desired curvature; and is provided so as to contact the concave surface of the wall portion And a microlens having a second refractive index higher than the first refractive index and filled in each region surrounded by the wall portion so as to correspond to the photoelectric conversion region. It includes a process of aligning and fixing.
With this configuration, since the microlens is formed and then adhered to the surface of the substrate on which the solid-state imaging device is formed, the microlens can be formed without damaging the solid-state imaging device.

The present invention provides, on a surface of a substrate, a photoelectric conversion unit including a plurality of photoelectric conversion regions constituting pixels, a charge transfer unit including a charge transfer electrode that transfers charges generated in the photoelectric conversion unit, Forming a microlens including a step of forming a peripheral circuit portion including a wiring layer connected to the charge transfer portion, and a step of forming a microlens on each of the photoelectric conversion regions on the substrate. A step of forming a lattice-like core body portion so as to stand up in an inter-lens region of each lens corresponding to the formation pitch of the lens surface of the microlens; and covering the core body portion; And a step of forming a wall portion having a concave surface curved with a desired curvature and a step of filling a member having a second refractive index in the wall portion to form a lens portion.
According to this configuration, since it can be formed without using a melting method, it is possible to shape the wall with good controllability, reduce variation, and reproducibly produce highly accurate and reliable microlenses. It becomes possible to form well.

According to the present invention, in the method for manufacturing a solid-state imaging device, prior to the step of forming the lens portion, etching is performed under an etching condition such that the etching rates of the wall portion and the base layer are equal, A step of transferring the shape to the base layer to form a wall portion made of the base layer.
According to this configuration, by forming the underlayer with a desired material, it is possible to shape the wall with high controllability by processing the shape by transfer, thereby reducing variation and achieving high accuracy. A highly reliable microlens can be formed with good reproducibility.

According to the present invention, in the method for manufacturing a solid-state imaging device, the step of forming the lens portion includes a step of flattening the surface.
According to this configuration, a solid-state imaging device having a flat surface can be formed with good controllability, and can be applied as an in-layer lens.

  According to the present invention, it is possible to provide a microlens having a desired curvature stably with reduced variation in shape. Therefore, it is possible to provide a solid-state imaging device that has excellent light collection characteristics, high sensitivity, and high reliability.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
1 and 2 are diagrams showing a solid-state imaging device on which the microlens according to Embodiment 1 of the present invention is mounted. FIG. 1 is a cross-sectional view, and FIG. 2 is a schematic plan view. FIG. 1 is a schematic cross-sectional view taken along line AA in FIG.
In the present embodiment, as shown in FIG. 1, a microlens M having a plurality of lens surfaces arranged to face each of a plurality of photoelectric conversion regions constituting a pixel is replaced with a lens surface of the microlens. A core body portion 61 provided in a lattice shape so as to stand up in an inter-lens region of each lens corresponding to the formation pitch, and a resin having a first refractive index formed so as to cover the core body portion 61 A wall portion 62 having a concave surface made of a coating film made of metal, and a second refractive index that is provided so as to contact the concave surface of the wall portion 62 and is filled in each region surrounded by the wall portion The resin lens unit 60 is provided. The lens part is composed of a high refractive index tourism resin having thermal or ultraviolet crosslinkability, a high refractive index photosensitive resin having a higher refractive index than the wall part 61, and a concave lens having a flat upper surface. Yes.

  As the material film having a high refractive index and photosensitivity, for example, a material film having a refractive index in the visible light region of about 1.6 is raised. Specific examples include one or a mixture of two or more of polyimide, polyalkyl methacrylate, polystyrene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, polyvinyl naphthalene, polyvinyl carbazole and the like. Further, in order to further improve the light collection efficiency, a material having a refractive index higher than these materials (preferably a refractive index difference is 0.4 or more), for example, a material having a refractive index of 2 or more. Specifically, an inorganic material, further an inorganic oxide, more specifically zinc oxide, titanium oxide, tin oxide, or the like may be added.

  These material films can be left only on the top of the photoelectric conversion portion by known photolithography and etching processes.

  In addition, it is desirable to use a photosensitive material for the structural material of the lens part and the wall part in order to simplify the process, but a material having no photosensitivity must be selected from the viewpoint of refractive index, translucency, and other characteristics. There may not be. In that case, it is possible to perform patterning by adding a known photolithography and etching process. In particular, when a non-photosensitive material is used for the lens portion, the lens portion can be formed in a self-aligned manner along the wall portion in the present embodiment, so that only a geometrically simple patterning process needs to be added. As a result, the non-photosensitive material is selected as the lens material that affects the light collection efficiency without degrading the accuracy of superimposition of the photoelectric conversion unit and the lens and the line width accuracy of the lens, which become more demanding as the pixel size becomes finer. be able to. Specifically, the material film may be left over the entire pixel region including a plurality of photoelectric conversion sites, and only the material film of the peripheral circuit portion such as the pad may be removed.

  The region other than the microlens has a usual structure, but prior to the description of the method of forming the microlens, the solid-state imaging device will be described first. In the solid-state imaging device used here, photodiodes 30 as photoelectric conversion units are arrayed on the surface of an n-type silicon substrate 1, and signal charges generated in the photodiodes 30 are arranged in the column direction (Y in FIG. 2). The charge transfer section 40 for transferring in the direction) is formed by meandering between a plurality of photodiode rows composed of the plurality of photodiodes 30 arranged in the column direction. Then, the odd-numbered photodiode rows are formed so as to be shifted in the direction of approximately half the array pitch of the photodiodes 30 arranged in the column direction with respect to the even-numbered photodiode rows.

  The charge transfer unit 40 includes a plurality of charge transfer channels 33 formed in the column direction of the surface portion of the silicon substrate 1 corresponding to each of the plurality of photodiode columns, and a charge transfer formed in the upper layer of the charge transfer channel 33. It includes an electrode 3 (first layer electrode 3a, second layer electrode 3b) and a charge readout region 34 for reading out charges generated in the photodiode 30 to the charge transfer channel 33. The charge transfer electrode 3 has a meandering shape extending in the row direction (X direction in FIG. 2) as a whole between a plurality of photodiode rows composed of a plurality of photodiodes 30 arranged in the row direction. . Here, the charge transfer electrode 3 has a single layer electrode structure in which a second layer electrode is formed on the first layer electrode via an interelectrode insulating film and is flattened by CMP, but is not limited to a single layer electrode structure. A two-layer electrode structure in which a part of the first layer electrode is covered with the second layer electrode may be used.

  As shown in FIG. 1, a p well layer 1P is formed on the surface of the silicon substrate 1, an n region 30b for forming a pn junction is formed in the p well layer 1P, and a p region 30a is formed on the surface. The photodiode 30 is configured, and the signal charge generated in the photodiode 30 is accumulated in the n region 30b.

  The photodiode 30 is formed with a charge transfer channel 33 composed of an n region at a slight distance (to the right in FIG. 1). A charge readout region 34 is formed in the p-well layer 1P between the n region 30b and the charge transfer channel 33.

A gate oxide film 2 is formed on the surface of the silicon substrate 1, and a first electrode 3 a and a second electrode 3 b are formed on the charge readout region 34 and the charge transfer channel 33 via the gate oxide film 2. The An interelectrode insulating film 5 is formed between the first electrode 3a and the second electrode 3b. Adjacent to the vertical transfer channel 33 (to the right in FIG. 1), a channel stop 32 made of a p ⁺ region is provided, and is separated from the adjacent photodiode 30.

  An insulating film 6 such as a silicon oxide film and an antireflection layer 7 are formed on the charge transfer electrode 3. Further, a light shielding film 8, an insulating film made of BPSG (borophosphosilicate glass), 9, P-SiN An insulating film (passivation film) 10 and an under-filter planarizing film 11 made of a silicon oxide film are formed. The light shielding film 8 is provided except for the opening of the photodiode 30. An upper filter flattening film 51 made of an insulating transparent resin or the like is provided on the upper layer of the color filter 50. A microlens M is provided on the upper layer.

  In the solid-state imaging device according to the present embodiment, signal charges generated in the photodiode 30 are accumulated in the n region 30b, and the accumulated signal charges are transferred in the column direction by the charge transfer channel 33, and the transferred signals are transferred. The charge is transferred in the row direction by a horizontal charge transfer path (HCCD) (not shown), and a color signal corresponding to the transferred signal charge is output from an amplifier (not shown). In other words, on the silicon substrate 1, a solid-state imaging device unit that is a region including a photoelectric conversion unit, a charge transfer unit, an HCCD, and an amplifier, and a peripheral circuit that is a region where peripheral circuits (PAD unit and the like) of the solid-state imaging device are formed. Are formed to constitute a solid-state imaging device.

  According to the above configuration, the lens portion 60 is formed by filling the wall portion 62 that has been processed in advance with the resin, thereby reducing variation in shape and providing a microlens having a stable and constant shape. It becomes possible to do. Moreover, since the wall part 62 is comprised with resin formed so that the core part 61 may be covered, shape control becomes easy by application | coating, without passing through a fusion | melting process. Therefore, the round shape of the surface can be controlled well and the controllability is greatly improved as compared with the conventional microlens that has obtained the lens shape itself by melting.

Next, the manufacturing process of the above-described solid-state imaging device will be described.
In this method, the lattice-shaped core body portion 61 made of the first resin is formed so as to stand up in the inter-lens region of each lens corresponding to the formation pitch of the lens surface of the microlens, and the core body portion 61 is formed. After forming the coating film 62 made of the second resin so as to cover the wall, the shape processing is performed so as to form a wall portion having a concave surface, and then the third resin is filled in the wall portion, and the lens portion 60 is formed.
In manufacturing, conventional methods other than the microlens manufacturing method are used. First, the manufacturing process up to the formation of the color filter will be described.
Impurities are introduced into the surface of the n-type silicon substrate 1 to form a p-well layer 1P, a charge transfer channel 33, a charge readout region 34, a channel stop layer 32, and the like, and then a gate oxide film 2 is formed. Subsequently, a first conductive film constituting the first layer electrode 3a is formed on the gate oxide film 2, and patterning is performed to form the first layer electrode 3a and peripheral circuit wiring. Next, an insulating film 5 made of a silicon oxide film is formed around the first layer electrode 3a, and a second conductive film constituting the second layer electrode 3b is formed thereon. Next, the second conductive film 3b is planarized by CMP and patterned to form the second layer electrode 3b. Next, after forming an insulating film 6 so as to cover these charge transfer electrodes 3, an n region 30b and a p region 30a in the photodiode region are formed, an antireflection film is formed, and light reception in the photodiode region is further performed. A light shielding film 8 is formed of a tungsten film or the like so as to open in the region. Next, an insulating film 9 is formed and planarized by high temperature reflow.

Next, after forming a contact hole in the upper part of the peripheral circuit of the insulating film 9, a metal film such as aluminum is formed and patterned to form a bonding pad (not shown). Then, a passivation film 10 made of a silicon nitride film is formed by the CVD method, and the passivation film on the bonding pad is selectively removed by etching to form an opening to expose the bonding pad. Thereafter, sintering is performed in an inert gas atmosphere containing H _2, and then a planarizing film 11 having a film thickness of 0.5 to 2.0 μm is formed by spin coating or scan coating. Here, in order to avoid confusion with other planarization films, this planarization film is referred to as an under-filter planarization film 11. Then, the color filter layers 50G, 50B, and 50R and the filter flattening film 51 are sequentially formed. The manufacturing process so far is a usual method. As the planarizing film 11 under the filter, a resist material transparent to visible light (for example, C series manufactured by FUJIFILM Electronics Materials Co., Ltd.) is used. However, when the film forming process of the filter base material layer of the color filter layer becomes high temperature, the under-filter planarizing film may be an inorganic film such as a silicon oxide film instead of an organic film. Moreover, when there are few unevenness | corrugations of a lower layer, there may not be a planarization film | membrane under a filter.

Next, the manufacturing process of the microlens will be described in detail with reference to the drawings.
3A to 3D are views showing a manufacturing process of a microlens. Here, for simplification, a region such as the insulating film 9 including the planarizing film 51 on the filter is shown as the intermediate layer 70.

First, as shown in FIG. 3A, a resist is applied on the intermediate layer 70 on the solid-state imaging device substrate on which the photoelectric conversion unit 30 and the charge transfer unit 40 are formed. Then, after patterning by photolithography, as shown in FIG. 3B, patterning is performed so as to form a grid shape having a width of 2, 3 microns and a height of 1 micron (see FIG. 7), and a core made of the first resist The body part 61 is formed. The lattice size can be reduced by using a well-known photolithography technique as the pixel size is reduced. In addition, by using a well-known photolithographic technique, the cross-sectional shape of the core body portion is forward-tapered, so that the conditions for pre-reflection of incident light are broadened, and the area of the region that does not contribute to the light collection on the top of the core body portion is reduced. As a result, the light collection efficiency to the photodiode can be improved.
Thereafter, as shown in FIG. 3C, the second resist is applied around the core portion 61 made of the first resist so as to have a desired curved shape, and a recess having a desired shape is formed. The wall 62 is obtained by covering with the second resist pattern.

  In this way, the concave portion of the obtained wall portion 62 is filled with a high refractive index photosensitive resin (third resin) which is a material having a higher refractive index, and as shown in FIG. A portion 60 is formed.

  As described above, according to the method of the present embodiment, the shape of the wall can be processed with good controllability, the variation can be reduced, and a highly accurate and reliable microlens can be formed with high reproducibility. It becomes possible.

  In this embodiment, the solid-state imaging device having a configuration in which photodiodes are arranged in a honeycomb shape has been described. However, the present invention is not limited thereto, and a configuration in which a plurality of photodiodes are arranged in a square lattice shape is described. The present invention can also be applied to other solid-state imaging devices.

  In the first embodiment, the resist pattern serving as the core for forming the wall 62 is patterned so as to form a lattice as shown in FIG. 9. In some cases, it is possible to form a lens surface with good light condensing characteristics without patterning by patterning into a shape and covering this with a second resist pattern.

  For example, as a modified example, as shown in FIG. 10, there are a lattice-shaped intermediate portion and a thickened shape. In this case, when the coating film (62) such as the second resist pattern is formed, the intermediate portion comes into contact first, and the flow at the tip of the coating film stops here, so that a curved surface with a smaller curvature radius is formed. be able to.

  As another modified example, as shown in FIG. 11, it is also effective to shape the core body portion 61 composed of the first resist pattern or the like while leaving a circular portion. In this case, when coated with a coating film such as the second resist pattern, since the flow on the base surface stops evenly flowing and the flow distance on the base surface is equal, a curved surface with less variation is formed. Can do.

  As another modified example, as shown in FIG. 12, it is also effective to shape-process the core part 61 composed of the first resist pattern and the like while leaving the octagonal part. In this case, since the flow distance of the coating film on the photodiode becomes uniform corresponding to the octagonal photodiode, the variation can be further reduced.

  Furthermore, the coating film is coated with a resist pattern made of the second resin so as to cover the core portion, but an inorganic film such as SOG may be formed by coating. Furthermore, a film covering the core part may be formed by CVD. In addition, as a filler constituting the lens surface, an inorganic film such as a high refractive index inorganic polymer to which zinc oxide, titanium oxide, tin oxide or the like is added may be filled in the wall instead of the resin. .

(Embodiment 2)
In the first embodiment, the wall portion is made of resin, but in this embodiment, the wall portion is made of a silicon oxide film 64, that is, an inorganic film, as shown in FIG. The lens portion is composed of a silicon nitride film 63. A lens formed with this configuration can be applied as an intralayer lens under a color filter. Others are formed in the same manner as the solid-state imaging device shown in the first embodiment.
In manufacturing, a silicon oxide film 64 formed by a CVD method is formed as a base layer, and a resist pattern R1 corresponding to the core portion 61 is formed on the silicon oxide film 64 in the same manner as in the process shown in FIG. After the shape processing is performed, the second resist pattern R2 corresponding to the wall portion is covered, and this is used as a mask so that the etching rates of the resist patterns R1 and R2 and the silicon oxide 64 as the underlayer become equal. Etching is performed under the conditions, and the shape of the resist pattern is transferred to the base layer to form the wall portion 64 made of the base layer.
According to this configuration, by forming the underlayer with a desired material, it is possible to shape the wall with high controllability by processing the shape by transfer, thereby reducing variation and achieving high accuracy. A highly reliable microlens can be formed with good reproducibility.

Next, the manufacturing process of this microlens will be described.
FIGS. 5A to 5D are views showing a manufacturing process of a microlens. Here, for simplification, a region such as the insulating film 9 including the planarizing film 51 on the filter is shown as the intermediate layer 70.

First, as shown in FIG. 5A, a silicon oxide film 62 is formed as a base layer by a CVD method on the intermediate layer 70 on the solid-state imaging device substrate on which the photoelectric conversion unit 30 and the charge transfer unit 40 are formed. A photoresist R1 is applied to the upper layer. Then, after patterning by photolithography, as shown in FIG. 5B, patterning is performed so as to form a lattice shape having a width of 2 to 3 microns and a height of 1 micron.
Thereafter, a second resist pattern is applied, and a pattern of this resist R2 is formed so as to have a desired curved shape as shown in FIG.

  In this way, using the obtained resist R1 and R2 pattern as a mask, etch back is performed under etching conditions such that the etching rates of the resist R2 and the silicon oxide film are equal, and the resist R1 and R2 pattern is oxidized. As shown in FIG. 5D, the wall portion 64 is formed by transferring to silicon.

Then, as shown in FIG. 6A, a silicon nitride film 63 is formed on the wall portion 62 by the CVD method.
Further, as shown in FIG. 6B, a resist R3 is applied to the upper layer and flattened.
Then, as shown in FIG. 6C, the microlens obtained by filling the concave surface of the wall portion 64 made of the silicon oxide film with the silicon nitride film 63 by performing resist etch back to flatten the surface. Complete.

  In the present embodiment, since the microlens is formed by filling the concave portion of the wall portion formed of the silicon oxide film with the silicon nitride film to form the lens portion 63, the manufacturing variation is suppressed, and the optical lens is optically formed. Properties and mechanical strength are improved. In addition, since the element portion is covered with a two-layer film of a silicon oxide film and a silicon nitride film, insulation and moisture resistance can be improved.

  In addition, if the resist pattern before fluidization for forming the wall portion and the coating process are simulated at the design stage to determine the optimum pattern according to the material, even if the pixel structure becomes complicated It is also possible to easily improve the quality of the lens.

  In the above embodiment, the microlens is formed on the upper layer after the solid-state image sensor is formed on the semiconductor substrate. However, the microlens layer is formed as a separate body, and this is adhered to the solid-state image sensor substrate. You may make it do.

(Embodiment 3)
In the first embodiment, the wall portion is made of resin. In this embodiment, as shown in FIG. 7, the core portion 65 made of a silicon oxide film is covered with a coating film 66 such as an SOG film. A wall portion is formed, and the concave portion is filled with a lens portion 63 made of a high refractive index inorganic polymer to which zinc oxide, titanium oxide, tin oxide or the like is added. Others are formed in the same manner as the solid-state imaging device shown in the first embodiment. FIGS. 8A to 8D show the manufacturing process.

At the time of manufacture, a silicon oxide film 65 is formed on the surface of the substrate on which the intermediate layer 70 is formed by the CVD method as shown in FIG. 8A, and patterned by photolithography, and then oxidized as shown in FIG. 8B. A lattice-shaped core body made of the silicon film 65 is formed. Then, as shown in FIG. 8 (c), an SOG film 66 is formed so as to cover the core part to obtain a desired recess.
Then, as shown in FIG. 8D, a lens portion 63 made of a high refractive index film such as a silicon nitride film is formed in the recess.
According to this configuration, the lens can be formed with good controllability by the inorganic film, and the reliability can be improved.
Further, the core part is not limited to the rectangular pattern, and may be formed to have an inclined surface using isotropic etching.

  According to the microlens of the present invention, shape variation can be reduced and high quality can be achieved. Therefore, the microlens is useful as a color filter for a solid-state imaging device in an electronic device such as a mobile phone.

Structure explanatory drawing of the solid-state image sensor using the microlens of Embodiment 1 of this invention 1 is a plan view of a solid-state imaging device according to a first embodiment of the present invention. The figure which shows the manufacturing process of the solid-state image sensor of this Embodiment 1. Structure explanatory drawing of the solid-state image sensor using the micro lens of Embodiment 2 of this invention The figure which shows the manufacturing process of the solid-state image sensor of Embodiment 2 of this invention. The figure which shows the manufacturing process of the solid-state image sensor of Embodiment 2 of this invention. The figure which shows the solid-state image sensor of Embodiment 3 of this invention. The figure which shows the manufacturing process of the solid-state image sensor of Embodiment 3 of this invention. The figure which shows the resist pattern used for the shape process of the micro lens of Embodiment 1 of this invention The figure which shows the modification of the resist pattern used for the shape process of the micro lens of Embodiment 1 of this invention The figure which shows the modification of the resist pattern used for the shape process of the micro lens of Embodiment 1 of this invention The figure which shows the modification of the resist pattern used for the shape process of the micro lens of Embodiment 1 of this invention The figure which shows the solid-state image sensor of a prior art example The figure which shows the solid-state image sensor of a prior art example

Explanation of symbols

1 n-type silicon substrate 2 gate oxide film 3a first electrode 3b second electrode 5 interelectrode insulating film 6 insulating film 7 antireflection layer 8 light shielding film 9 insulating (BPSG) film 10 passivation film 11 planarizing films 50B and 50R , 50G color filter 51 planarizing film 60 on the filter micro lens (lens part)
61 Core part 62 Wall part 63 Lens part 64 Wall part 65 Core part 66 Wall part 70 Intermediate layer 80 showing an area such as the insulating film 9 including the planarizing film 51 on the filter Intermediate layer showing an area containing the insulating film 9 R1 resist pattern R2 resist pattern R3 resist pattern

Claims (22)

A microlens having a plurality of lens surfaces arranged to face each of a plurality of photoelectric conversion regions constituting a pixel,
Corresponding to the formation pitch of the lens surfaces of the microlenses, a core body portion provided in a lattice shape so as to stand in an inter-lens area of each lens, and a first body provided to cover the core body portion A wall having a concave surface having a refractive index;
A microlens comprising: a lens portion that is provided in contact with the concave surface of the wall portion, is filled in each region surrounded by the wall portion, and has a second refractive index higher than the first refractive index. . The microlens according to claim 1,
The wall portion is a microlens made of a coating film. The microlens according to claim 2,
The core is a microlens made of a first resin. The microlens according to claim 2,
The core is a microlens made of an inorganic film. The microlens according to any one of claims 1 to 4,
The wall portion is a microlens made of a second resin. The microlens according to any one of claims 1 to 4,
The wall portion is a microlens made of an inorganic film. The microlens according to any one of claims 1 to 6,
The lens portion is a microlens made of a third resin. The microlens according to any one of claims 1 to 6,
The lens part is a microlens made of an inorganic film. The microlens according to claim 1,
The wall portion is a microlens made of an SOG film, and the lens portion is made of a high refractive index inorganic polymer. The microlens according to claim 1,
A microlens in which a difference in refractive index between the wall portion and the lens portion is 0.4 or more. The microlens according to claim 1,
A microlens having a refractive index of the core portion smaller than that of the wall portion. The microlens according to claim 1,
A microlens in which a cross-sectional shape of the core body portion is a forward tapered shape. A method of manufacturing a microlens that is disposed so as to face each of a plurality of photoelectric conversion regions constituting a pixel and includes a plurality of lens surfaces,
Forming a lattice-shaped core pattern so as to stand up in an inter-lens region of each lens corresponding to the formation pitch of the lens surface of the microlens;
Coating the core with a coating film, forming a wall having a first refractive index and having a concave surface curved with a desired curvature; and
Filling each region surrounded by the wall with a member having a second refractive index, and forming a lens portion. It is a manufacturing method of the micro lens according to claim 13,
Prior to the step of forming the lens portion, etching is performed under an etching condition such that the etching rates of the wall portion, the core portion, and the underlayer are equal, and the shape of the wall portion is transferred to the underlayer. A method of manufacturing a microlens, including a step of forming a wall portion made of an underlayer. The method of manufacturing a microlens according to claim 13 or 14,
The step of forming the lens portion is a method of manufacturing a microlens including a step of flattening the surface. A photoelectric conversion unit including a plurality of photoelectric conversion regions constituting a pixel, a charge transfer unit including a charge transfer electrode that transfers charges generated in the photoelectric conversion unit, and a wiring connected to the charge transfer unit On the surface of the substrate on which the peripheral circuit part including the layer is formed,
A solid-state image sensor on which the microlens according to claim 1 is mounted. A photoelectric conversion unit including a plurality of photoelectric conversion regions constituting a pixel, a charge transfer unit including a charge transfer electrode that transfers charges generated in the photoelectric conversion unit, and a wiring connected to the charge transfer unit On the surface of the substrate on which the peripheral circuit part including the layer is formed,
Corresponding to the formation pitch of the lens surfaces of the microlenses, a core body portion provided in a lattice shape so as to stand in an inter-lens area of each lens, and a first body provided to cover the core body portion A wall having a concave surface having a refractive index;
A microlens comprising: a lens portion that is provided in contact with the concave surface of the wall portion, is filled in each region surrounded by the wall portion, and has a second refractive index higher than the first refractive index. A method for manufacturing a solid-state imaging device, including a step of aligning and fixing so as to correspond to the photoelectric conversion region. A photoelectric conversion unit having a plurality of photoelectric conversion regions constituting pixels on a surface of a substrate, a charge transfer unit having a charge transfer electrode for transferring charges generated by the photoelectric conversion unit, and the charge transfer unit Forming a peripheral circuit portion including a wiring layer connected to
Forming a microlens on each of the photoelectric conversion regions on the substrate,
Forming the microlens,
Forming a lattice-shaped core body portion so as to stand up in an inter-lens region of each lens corresponding to the formation pitch of the lens surface of the microlens;
Coating the core with a coating film, forming a wall having a first refractive index and having a concave surface curved with a desired curvature; and
A step of filling a region surrounded by the wall with a member having a second refractive index, and forming a lens portion. It is a manufacturing method of the solid-state image sensing device according to claim 18,
Prior to the step of forming the lens portion, etching is performed under an etching condition such that the etching rates of the core body portion and the wall portion and the underlayer are equal, and the shape of the wall portion is transferred to the underlayer. A method for manufacturing a solid-state imaging device, including a step of forming a wall portion made of an underlayer. A method for manufacturing a solid-state imaging device according to claim 18 or 19,
The step of forming the lens portion is a method for manufacturing a solid-state imaging device, including a step of flattening the surface. A method of manufacturing a solid-state imaging device according to any one of claims 18 to 20,
The method of manufacturing a solid-state imaging device, wherein the step of forming the wall portion includes a step of forming the wall portion so as to be larger than the refractive index of the core body portion. A method of manufacturing a solid-state imaging device according to any one of claims 18 to 20,
The step of forming the core part includes a method of manufacturing a solid-state imaging device, including a step of processing the cross-sectional shape to be a forward taper.

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