JPH07105481B2 - Method of manufacturing solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for manufacturing a solid-state imaging device in which element sensitivity is improved by using a microlens.

(Prior Art) Generally, a solid-state image pickup device is configured by arranging a plurality of pixels each including a solid-state image pickup element. In one solid-state image pickup element, incident light is converted into an electric signal by a photosensitive portion such as a photodiode, and an output signal is output. In such a solid-state image sensor, a microlens is provided above the light-receiving portion to increase the light-receiving sensitivity without increasing the size of the light-receiving portion of the photodiode, and external light is focused on the photosensitive portion by the microlens. It is generally done.

This will be described with reference to FIG. 3. On the semiconductor substrate 1, a photodiode 2 as a photosensitive portion that converts incident light into an electric signal and outputs the signal, and a photodiode 2 in each column. Bonding pad portions 3 are formed at both ends, and a passivation film 4 and a filter layer 5 are sequentially laminated on the upper surface of the bonding pad portion 3 except above the bonding pad portions 3. A microlens 6'having a convex lens shape is provided above the photodiode 2 on the upper surface of the filter layer 5. The microlens 6'collects light and collects the collected light. It is configured to increase this sensitivity by making it incident on the diode 2.

The microlens 6'is generally made of gelatin, casein or acrylic resist due to the following manufacturing restrictions.

In the above solid-state imaging device, since the resist above the bonding pad 3 needs to be removed as described above, this manufacturing is generally performed as follows.

That is, a photosensitive resist is used as the passivation film 4, the intermediate film for preventing color mixture bleeding interposed between the color dyeing layers in the filter layer 5, and the protective film disposed on the upper surface of the filter layer 5, After applying these films, the film is developed each time, and the resist located above the bonding pad portion 3 is removed each time.
Of the substrate shown in FIG. 3 except for the microlens 6 ', a substrate portion is formed, and then the microlens 6'is patterned at a predetermined position above the photodiode portion 2 to further form this microlens 6'. When a gelatin-based or casein-based resist is used, the upper surface is covered with a protective film, and when an acrylic-based resist is used, the surface is melted, and the solid-state imaging device shown in FIG. It was manufactured.

If a microlens is to be formed by dry etching, the resist to be masked needs to be thickened, which has the drawback of impairing the lens effect as a microlens. Selection of the resist material and inexpensive microlens Was generally difficult to make.

That is, since the microlens is formed on the upper surface of the filter layer, the process of forming the microlens has a great relation to the state of the surface of the filter layer. Therefore, it is very difficult to form a microlens of a desired shape when removing the resist above the bonding pad portion by dry etching, and a positive resist or the like is used, and bonding is performed by dry etching using this as a mask. When the resist on the pad is removed, it is difficult to remove the positive resist after this removal, and when an inorganic transparent film is used as the resist and the resist on the bonding pad is removed by dry etching as the mask, This is because this film has a fairly good flatness, so that the effect of the microlens is significantly impaired by this film.

Therefore, the formation of the microlenses by dry etching is not generally performed, and the microlenses are limited to gelatin-based, casein-based, or acrylic-based resists as described above. Met.

(Problems to be Solved by the Invention) However, in the conventional example, since the microlenses are formed of a gelatin-based, casein-based, or acrylic-based resist, their refractive index is generally small, and when microlenses are not used. Compared with, the sensitivity improvement is about 1.5 times at most, and it was not possible to reduce the smear phenomenon that the image had a whitish tail when shooting a bright subject.

Further, in the above-mentioned manufacturing method, it is necessary to develop the passivation film, the film for preventing color bleeding, the protective film, etc. every time, not only the material is limited but also the number of steps is increased, and the acid used for dyeing is also used. As a result, the aluminum light-shielding film provided on the upper surface of the passivation film may be corroded.

In view of the above, the present invention aims to improve the element sensitivity by using a resist having a larger refractive index by forming a microlens by dry etching, and to form a microlens of a desired shape without increasing the number of steps. It is an object of the present invention to provide a product that can be manufactured at low cost.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above object, a method for manufacturing a solid-state imaging device according to the present invention is a method of laminating a filter layer on an upper surface of a semiconductor substrate on which a photosensitive portion and a bonding pad portion are formed, and bonding A layer of a transparent resist is formed on the upper surface of the resist except above the pad portion, a positive resist is patterned on the resist above the photosensitive portion, and dry etching is performed to form a micro resist with the transparent resist. The lens is formed, and the resist above the bonding pad portion of the filter layer is removed by using the transparent resist as a mask.

(Operation) According to the present invention configured as described above, the microlens can be formed by dry etching using a transparent resist material coated on the upper surface of the filter layer, and thus a resist having a high bending rate can be formed by using a microlens. It is used as a lens material to increase the bending rate as a microlens, and the resist above the bonding pad portion can be removed by using the resist forming the microlens as a mask, so the number of steps can be reduced. .

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 shows a solid-state image pickup element manufactured by a manufacturing method according to an embodiment of the present invention. A photosensitive section for converting incident light into an electric signal and outputting the signal is formed on a semiconductor substrate 1. 2 and the bonding pad portions 3 are formed at both ends of each row of the photodiodes 2, respectively, and a passivation film 4 and a filter layer are formed on the upper surface of the photodiode 2 except above the bonding pad portion 3. 5 are sequentially stacked. A microlens 6 in the shape of a convex lens is provided above the photodiode 2 on the upper surface of the filter layer 5,
Light is collected by the microlens 6 and the collected light is made incident on the photodiode 2 to enhance the sensitivity.

The microlens 6 is formed by dry etching a silicon-based or polystyrene-based resist, thereby improving the sensitivity and reducing the smear phenomenon.

That is, when the microlens 6 is formed by using, for example, a silicon-based resist as the material, the element sensitivity can be improved about twice as compared with the case where the microlens is not provided.

A method of manufacturing the image pickup device will be described with reference to FIG.

First, as shown in FIG.
A photodiode 2 as a photosensitive portion that converts incident light into an electric signal and outputs the signal, and a bonding pad portion 3 located at both ends of each row of the photodiode 2 are formed on the upper surface of the photodiode 2. The bonding pad portion 3 is exposed to form a passivation film 4, and a filter layer 5 is sequentially laminated on the entire upper surface thereof.
The surface 5a is provided with irregularities according to the shape of the microlens 6 formed here.

At this time, the protective film of the color fill layer 5 covers the bonding pad portion 3, and therefore the bonding pad portion 3 is not exposed to other acid or the like.

In this state, the upper surface of the filter layer 5 has photosensitivity, as shown in FIG. For example, a polystyrene-based transparent microlens forming resist 6a is applied to a thickness of about 2 μm, and the upper portion of the bonding pad portion 3 is removed by development.

Then, as shown in FIG.
It is applied to a thickness of about 7 μm and patterned into a desired shape so that the positive resist 7 remains at a predetermined position where the microlens 6 is formed, that is, above the photodiode 2, and in this state, in O ² plasma. Then, dry etching is performed.

Then, by this dry etching, the positive resist 7
Is gradually removed from above, and the resist 6a is gradually removed from the exposed portion of the microlens forming resist 6a toward the center of the positive resist 7 to form a convex lens-shaped microlens 6 with the resist 6a. At the same time, the resist above the bonding pad portion 3 of the filter layer 5 is removed using the microlens forming resist 6a as a mask to manufacture the solid-state imaging device shown in FIG.

As another method, in FIG. 2 (b), a silicon-based resist is used as the transparent microlens molding resist 6a, and in FIG. The positive resist 7 is also patterned on the upper side, and in this state, etching is performed in a plasma with a Freon-based gas to form the shape of the upper surface of the microlens 6, and the half-formed microlens 6 is used as a mask for O ₂ The microlens 6 is wholly formed by performing dry etching in plasma, and the resist above the bonding pad portion 3 of the filter layer 5 is removed to manufacture the solid-state imaging device shown in FIG. You can also do so.

〔The invention's effect〕

Since the present invention is configured as described above, it is possible to use a polystyrene-based or silicon-based resist as the material of the microlens. In this case, since the bending rate becomes large, the light receiving sensitivity of the conventional lens can be increased. Not only can it be improved further than with a microlens, but it is also possible to reduce the smear phenomenon that causes a whitish tail to appear when shooting a bright subject.

Further, the light receiving sensitivity is not lowered by the flattening at the time of fixing by dropping the resin in the assembly process in the subsequent process, and the heat resistance and the light resistance of the filter layer are improved.

Further, the resist above the bonding pad portion can be removed by dry etching. Therefore, the aluminum light-shielding film is prevented from being corroded, and development is prevented each time, so that the number of steps is reduced and the amount of developer used is reduced. It is possible to reduce.

Moreover, since the formation of the microlens and the removal of the resist above the bonding pad portion are performed at the same time, there is an effect that the process can be further shortened.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a solid-state imaging device manufactured by a manufacturing method according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a step sequence in the manufacturing method according to one embodiment, and FIG. It is sectional drawing which shows a solid-state imaging device. 1 ... Semiconductor substrate, 2 ... Photodiode, 3 ... Bonding pad section, 4 ... Passivation film, 5 ...
... Filter layer, 6 ... Microlens, 6a ... Microlens forming resist, 7 ... Positive resist, 6 '...
Conventional microlens.

Claims (1)

[Claims] 1. A filter layer is laminated on an upper surface of a semiconductor substrate on which a photosensitive portion and a bonding pad portion are formed, and a transparent resist layer is formed on the upper surface of the semiconductor substrate except above the bonding pad portion. Patterning a positive resist located above the photosensitive portion and performing dry etching to form a microlens with the transparent resist, and using the transparent resist as a mask, the resist above the bonding pad portion of the filter layer. A method for manufacturing a solid-state imaging device, comprising: