JPH02103962A - Solid-state image sensing device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain high sensitivity and to make smear and flare less by forming a microlens for light sensitive picture elements with convex and concave lenses having required refractive indexes. CONSTITUTION:Light is condensed on each photodiode 2 in a plurality of light sensitive parts through a microlens 6. The microlens 6 is composed of a convex lens 6b comprising resist having a large refractive index and a concave lens 6a comprising resist having a small refractive index. This microlens is different from the case wherein only a convex lens that cannot condense sufficient light on the photodiode 2 and has much smear and flare is used in forming the microlens. In the microlens in the present invention, the sensitivity is enhanced, and the smear and the flare can be made less.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention relates to a solid-state imaging device and a method for manufacturing the same, and in particular, to improving element sensitivity by using an improved microlens, and improving smear and flare reduction. The present invention relates to a solid-state imaging device and a method for manufacturing the same in which generation is minimized.

(Prior Art) In general, a solid-state imaging device is constructed by arranging a plurality of pixels made up of solid-state imaging devices.In one solid-state imaging device, incident light is converted into an electrical signal by a photosensitive section made of a photodiode or the like. It is designed to convert and output the signal. In such a solid-state image sensor, in order to increase the light-receiving sensitivity without increasing the size of the light-receiving part of the photodiode, which is the light-sensitive part, a microlens is provided above the light-sensitive part, and this microlens directs external light to the light-sensitive part. It is common practice to focus the light.

This will be explained with reference to FIGS. 7 and 8.

In FIG. 7, inside a semiconductor substrate 1, a plurality of photodiodes 2 are formed as photosensitive parts with upward openings, and the upper surface of the photodiodes 2 is covered with a passivation film 3. A filter layer 4 is formed. The upper surface of this color filter layer 4 is covered with a flat transparent layer 5 made of, for example, acrylic resist, and furthermore, convex lenses are arranged on the upper surface of this transparent layer 5 at positions corresponding to the respective photodiodes 2. The microlens 6' is formed of, for example, an acrylic resist. As a result, a solid-state imaging device was constructed in which a plurality of pixels were arranged so that external light was focused on each photodiode 2 by each microlens 6'.

In FIG. 8, a plurality of photodiodes 2 as photosensitive parts are formed inside a semiconductor substrate 1, and an anti-reflection film 7 is provided between each photodiode 2 on the upper surface of the semiconductor substrate 1. This upper surface is covered with a transparent layer 5 such as an acrylic resist, and a microlens 6', which is a convex lens, is formed at a position corresponding to each photodiode 2 using, for example, an acrylic resist. As a result, a solid-state imaging device was constructed in which a plurality of pixels were arranged so that external light was focused on each photodiode 2 by each microlens 6'.

(Problem to be Solved by the Invention) However, in the above conventional example, since external light was focused using a microlens consisting only of convex lenses,
This light condensation becomes insufficient, and as shown in FIGS. 7 and 8, not only is it impossible to perform sufficient condensation, but also
Generally, light is not focused at the center of the photodiode (photosensitive section) but enters obliquely, which causes problems such as large smears and flare caused by surface reflections.

Generally, when forming a microlens, it is necessary to thicken the film and create a large taper in order to effectively focus light, but resist generally forms a gentle taper when the film is thick. Therefore, effective light collection cannot be performed.

In view of the above, the present invention can realize high sensitivity,
Moreover, it is an object of the present invention to provide a solid-state imaging device with small smear and flare, and a manufacturing method thereof.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the solid-state imaging device of the present invention includes a photosensitive section formed on a semiconductor substrate, and a device located above the photosensitive section that directs external light to the photosensitive section. In a solid-state imaging device comprising a plurality of photosensitive pixels arranged with a microlens for condensing light, the microlens is arranged above and below a convex lens made of a resist with a large refractive index and a concave lens made of a resist with a smaller refractive index than the convex lens. It is constructed by laminating the two lenses together.

Further, the solid-state imaging device described above includes a step of forming a plurality of photosensitive parts in a semiconductor substrate, a step of forming a concave lens with a transparent resist layer at an upper position corresponding to each of the photosensitive parts, and a process of forming a concave lens on the upper surface of the concave lens. A convex lens can be manufactured by forming a convex lens using a transparent resist layer having a higher refractive index than the concave lens forming resist layer.

(Function) According to the present invention configured as described above, external light is first condensed by a convex lens, and further condensed by a concave lens having a smaller curvature than the convex lens. As a result, the light condensing power of the microlens that combines the convex lens and concave lens can be much higher, for example, about twice as much as that of a convex lens alone. can be focused on the center of the photodiode.

Moreover, by arbitrarily selecting resists for forming the convex lens and the concave lens, manufacturing can be easily performed.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment, in which a plurality of photodiodes 2 are formed inside a semiconductor substrate 1 as photosensitive portions opening upward, and each photodiode of the semiconductor substrate 1 is A light antireflection film 7 is provided between the diodes 2.2. Although not shown, it is of course possible to provide a passivation film on the upper surface of the substrate.

This configuration is almost the same as that shown in FIG. 7 above, but differs in the following points.

That is, on the upper surface of the semiconductor substrate 1, a resist 6a' located above each photodiode 2 and having a smaller refractive index than the convex lens 6b described below, for example, an acrylic resist 6a' having a refractive index of about 1.4, is formed. The formed concave lens 6a,
On the upper surface of this concave lens 6a, a convex lens 6b made of a styrene resist 6b' having a refractive index of about 1.7, for example.
A microlens 6 is formed.

As a result, two-stage light condensing is performed in which the light condensed by the convex lens 6b with a large refractive index is first provided with a condensing effect, and then the light condensed by the convex lens 6b is further condensed with the concave lens 6a which has a smaller refractive index than the convex lens 6b. It is configured as follows.

In this way, by performing two-stage light focusing, the light focusing effect is much improved compared to the conventional microlens made of only convex lenses. By directing the light to the center of each foot diode 2, smear and flare can be reduced.

FIG. 2 shows a second embodiment, in which a plurality of photodiodes 2 are formed as photosensitive parts inside a semiconductor substrate 1, and the upper surface of this semiconductor substrate 1 is covered with a passivation film 3. At the same time, this passivation film 3
A color filter layer 4 is formed on the upper surface of.

Further, on the upper surface of this color filter layer 4, a resist having a refractive index smaller than that of the convex lens 6b described below, for example, an acrylic resist having a refractive index of about 1.4, is placed above each photodiode 2 as described above. A microlens 6 is formed of a concave lens 6a made of a resist 6a' and a convex lens 6b made of a styrene resist 6b' having a refractive index of about 1.7 on the upper surface of the concave lens 6a.

As a result, similarly to the first embodiment, the light collection sensitivity is increased, and the collected light is placed in the center of each photodiode 2, thereby reducing smear and flare. .

FIG. 3 shows a third embodiment. The difference from the first embodiment is that the thickness of the anti-reflection film 7 is increased to optimize the shape of the concave lens 6a. That's what I did.

This shape takes into account the shape of the semiconductor substrate 1 in addition to the anti-reflection film 6a, so that the thickness of the anti-reflection film 7 does not need to be so thick. By setting the thickness of the anti-reflection film 7 on this substrate 1 to 1.2 μm, a sufficient concave lens 6a can be formed.
can be formed.

FIG. 4 shows a fourth embodiment, which differs from the second embodiment in that the top layer 8 is laminated on the upper surface of the color filter layer 4 at the upper position between each photodiode 2.
An anti-reflection JII film 7 is formed on the top surface of the anti-reflection film 7, and a concave lens 6a is formed to surround each anti-reflection film 7.

In this embodiment, similarly to the third embodiment, the thickness of the antireflection film 7 is approximately 1.2 μm, and a sufficient concave lens 6a can be formed.

This is because the concave lens 6a is located above the color filter layer 4 and the distance between the concave lens 6a and the photodiode 2 is sufficient, so there is no need to increase the film thickness so much.

Here, the color of each of the above-mentioned antireflection films 7 does not need to be black as long as the lens effect is sufficiently large, and even if the film is transparent, the flare will not be too large.

FIG. 5 shows the manufacturing method of the second embodiment shown in FIG. 2 above.

That is, a photodiode 2 is formed as a photosensitive part inside a semiconductor substrate 1, a passivation film 3 is applied on the upper surface of the photodiode 2, and a color filter layer 4 is patterned on the upper surface of the passivation film 3 (see FIG. 2(a)). ).

Then, on the upper surface of this color filter layer 4, an acrylic transparent resist 6a' having a refractive index of about 1.4, which is a resist for forming a concave lens, is applied to a thickness of about 1.5 μm, for example.
Furthermore, apply a positive resist 9 of about 0.5 μm on top of it.
Pattern a predetermined position (same <(b)). Thereafter, by using the positive resist 9 as a mask and performing plasma etching using, for example, 02, a concave lens 6a is formed using the resist 5a/.
Same figure (c).

Next, the refractive index of the concave lens is 1.4, which is greater than about 1.4.
A styrene-based resist 6b' for forming a convex lens having a refractive index of about 7 is applied, and a positive resist 10 is patterned at a desired position on the upper surface in the same manner as described above (FIG. 2(d)).
By using this positive resist 10 as a mask and forming a convex lens 6b using the resist 6b', a solid-state image pickup device including a microlens 6 consisting of a concave lens 6a having a small refractive index and a convex lens 6b having a larger refractive index than the concave lens 6a can be obtained. It configures the device.

Although the convex lens 6b is formed by dry etching, it goes without saying that it may be formed using other methods.

FIG. 6 shows a manufacturing method of the fourth embodiment shown in FIG. 4 above.

That is, a photodiode 2 is formed as a photosensitive part inside a semiconductor substrate 1, a passivation film 3 is applied on the upper surface of the photodiode 2, a color filter layer 4 is patterned on the upper surface of this passivation film 3, and a top layer is formed on this upper surface. The layers 8 are laminated, and the anti-reflection JII 7 is formed at a desired position on the upper surface of the top layer 8 to a thickness of, for example, about 1 to 2 μm (FIG. 4(a)).

Then, an acrylic transparent resist 6a' having a refractive index of about 1.4, which is a resist for forming a concave lens, is applied to the upper surface of the top layer 8 to a thickness of, for example, about 1.5 μm. is formed (Figure (b)).

Next, a styrene resist 6b' for forming a convex lens having a refractive index of about 1.7, which is larger than the refractive index of about 1.4 of the concave lens 6a, is applied, and a positive resist 10 is patterned at a desired position on the upper surface. (C)) By using this positive resist 10 as a mask and forming a convex lens 6b with the resist 6b', a microlens consisting of a concave lens 6a with a small refractive index and a convex lens 6b with a larger refractive index than this concave lens 6a is obtained. This constitutes a solid-state imaging device equipped with 6.

In addition, when removing the resist of the bonding pad, it can be removed at the same time as forming the convex lens 6b.

〔Effect of the invention〕

Since the present invention has the above-mentioned configuration, the microlens is constructed by stacking a convex lens with a large refractive index and a concave lens with a smaller refractive index than the convex lens above and below. It is possible to collect external light much more efficiently, and also to focus this collected light on the center of the photodiode, reducing smear and flare as much as possible and significantly improving sensitivity. Can be done.

Furthermore, since the lens effect can be improved by nearly twice that of conventional technology, it is possible to increase the degree of integration (
, by using styrene resist for the convex lens,
Heat resistance and light resistance can be improved.

In addition, by manufacturing microlenses by dry etching, it is not only possible to eliminate corrosion of the aluminum part and obtain a high-quality solid-state imaging device, but also by using a positive resist, microlenses with fine patterns can be manufactured. There is an effect that it can also be made to form.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views showing different embodiments of the present invention, FIG. 5 is a cross-sectional view showing the manufacturing method of the solid-state imaging device shown in FIG. 2 in order of process, and FIG. FIGS. 7 and 8 are cross-sectional views showing different conventional examples, respectively. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Photodiode (photosensitive part), 3... Passivation film, 4... Color filter layer, 6... Microlens, 6a... Concave lens, 6b...・Same convex lens, 7... Anti-reflection film.

Claims (1)

[Claims] 1. A plurality of photosensitive pixels each having a photosensitive area formed on a semiconductor substrate and a microlens positioned above the photosensitive area to focus external light onto the photosensitive area are arranged. In the solid-state imaging device, the microlens is constructed by stacking a convex lens made of a resist with a large refractive index and a concave lens made of a resist with a smaller refractive index than the convex lens vertically, and combining the two lenses. A solid-state imaging device. 2. A step of forming a plurality of photosensitive parts in a semiconductor substrate, a step of forming a concave lens using a transparent resist layer at an upper position corresponding to each of the photosensitive parts, and a resist layer for forming the concave lens on the upper surface of the concave lens. A method for manufacturing a solid-state imaging device, comprising the step of forming a convex lens using a transparent resist layer having a higher refractive index.