JPH01270362A - Solid-state image sensing device and manufacture thereof - Google Patents

Abstract

PURPOSE:To contrive the improvement of the sensitivity of an element and to make it possible to manufacture a microlens of a desired configuration at low cost without increasing the number of processes by a method wherein the microlens is formed into a transparent resist consisting of silicon, polystyrene and so on by dry etching. CONSTITUTION:Photodiodes 2 and a bonding pad part 3 are formed on a semiconductor substrate 1, the part 3 is exposed on the upper surface of this substrate to laminate in order a passivation film 4 and a filter layer 5, the surface 5a of the layer 5 is roughened conforming to the configuration of a microlens 6, which is formed on the surface 5a, a transparent resist 6a consisting of polystyrene, for example, is applied on the upper surface of the layer 5 and the film 4, the layer 4 and the resist 6a, which are located on the part 3, are removed by developing. Moreover, a positive resist 7 is coated, a dry etching is performed to form the convex lens-shaped microlens 6 with this resist 6a and the resist which is located on the layer 5 and is located over the part 3 is removed using the resist 6a as a mask to manufacture a solid-state image sensing device.

Description

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

(Prior Art) Generally, a solid-state imaging device is configured by arranging a plurality of pixels made of solid-state imaging elements. In one solid-state image sensor, incident light is converted into an electrical signal by a photosensitive section made of a photodiode or the like, and an output signal is generated. In such solid-state image sensors, in order to increase the light-receiving sensitivity without increasing the size of the light-receiving part of the photodiode, a microlens is provided above the light-receiving part, and this microlens focuses external light onto the light-receiving part. It is common practice to do so.

To explain this based on FIG. 3, on the semiconductor substrate 1 there is a photodiode 2 as a photosensitive part that converts incident light into an electric signal and outputs the signal, and each column of the photodiode 2 has a 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 portions 3 except above the bonding pad portions 3. A microlens 6' in the shape of a convex lens is provided on the upper surface of the filter layer 5, and is located above the photodiode 2. The microlens 6' collects light and converts the collected light into a photo. It is configured to increase this sensitivity by entering the diode 2.

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

In the above-mentioned solid-state imaging device, since it is necessary to remove the resist above the bonding pad 3 as described above, the manufacturing thereof has generally been performed as follows.

That is, a photosensitive resist is used as the passivation film 4, the intermediate film interposed between the color dyeing layers in the filter layer 5 to prevent color mixture bleeding, and the protective film disposed on the upper surface of the filter layer 5. After applying these films, by developing each time and removing the resist located above the bonding pad portion 3 each time,
A substrate part excluding the microlens 6' of the one shown in FIG. When a gelatin-based or casein-based resist is used as a resist, a protective film is placed on the top surface of the resist, or when an acrylic resist is used, the surface is melted to form the solid-state imaging device shown in Figure 3. It was intended to manufacture.

In addition, when attempting to form microlenses by dry etching, it is necessary to thicken the masking resist, which has the disadvantage of impairing the lens effect as a microlens. was generally difficult to make.

That is, since the microlens is made on the top surface of the filter layer, the process of making it has a great deal to do with the condition of the surface of the filter layer. For this reason, it is very difficult to form a microlens in the desired shape when removing the resist above the bonding pad by dry etching, and using a positive resist etc. as a mask, dry etching removes the bonding pad. When removing the resist from the bonding pad area, it is difficult to peel off the positive resist after this removal, and furthermore, when an inorganic transparent film is used as the resist and the resist from the bonding pad area is removed by dry etching as a mask, it is difficult to peel off the positive resist after this removal. ,
This is because this film has fairly good flatness, so the effect of the microlens is significantly impaired by this film.

For this reason, the microlenses described above are not generally formed by dry etching, and the microlenses are currently limited to gelatin-based, casein-based, or acrylic-based resists as described above. Met.

(Problem to be Solved by the Invention) However, in conventional examples, microlenses are formed of gelatin-based, casein-based, or acrylic-based resists, so their refractive index is generally small, and when microlenses are not used, Not only is the sensitivity only limited to an improvement of about 1.5 times at most, but it also fails to reduce the smear phenomenon that causes whitish tails in the top and bottom when photographing bright objects.

In addition, in the above manufacturing method, it is necessary to develop the bashvation film, the film that prevents color mixture bleeding, and the protective film each time, which not only limits the materials used but also increases the number of steps. There is a problem in that the aluminum light-shielding film provided on the upper surface of the passivation film may be corroded by the acid.

In view of the above, the present invention aims to improve element sensitivity by using a resist with a higher refractive index by forming microlenses by dry etching, and to form microlenses in a desired shape without increasing the number of steps. The purpose is to provide products that can be manufactured at low cost.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, a solid-state imaging device according to the present invention includes a photosensitive portion and a bonding pad portion formed on a semiconductor substrate, and a filter layer is formed on the upper surface of the photosensitive portion and a bonding pad portion except above the bonding pad portion. In a solid-state imaging device in which a microlens is placed above the photosensitive area, the microlens is formed by dry etching a transparent resist such as silicone or polystyrene. In this method, a filter layer is laminated on the upper surface of a semiconductor substrate on which a photosensitive area and a bonding pad area are formed, a transparent resist is applied to this upper surface except above the bonding pad area, and the photosensitive area is layered on top of this resist. By patterning the positive resist located above and performing dry etching, a microlens is formed using the transparent resist, and the resist above the bonding pad portion of the filter layer is removed using the transparent resist as a mask. This is what I did.

(Function) According to the present invention configured as described above, the microlens can be made by dry etching using a transparent resist coated on the upper surface of the filter layer. It is used as a material for microlenses to increase the curvature of the microlenses, and the resist above the bonding pad can be removed using the resist constituting the microlenses as a mask, reducing the number of steps. be able to.

(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 sensor. On a semiconductor substrate 1, there is a photodiode 2 as a photosensitive part that converts incident light into an electrical signal and outputs the signal, and each of the photodiodes 2 Bonding pad portions 3 are formed at both ends of the row, and a passivation film 4 and a filter layer 5 are sequentially laminated on the upper surface of the bonding pad portions 3 except above the bonding pad portions 3. A microlens 6 in the shape of a convex lens is provided on the upper surface of the filter layer 5 and is located above the photodiode 2. The microlens 6 collects light, and the collected light is transmitted to the photodiode 2. The structure is configured to increase this sensitivity by making the beam incident on the beam.

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

That is, when the microlens 6 is formed using, for example, a silicon-based resist as a material, it is possible to improve the element sensitivity by about twice as much as when no microlens is provided.

A method of manufacturing the above imaging device will be explained based on FIG. 2.

First, as shown in FIG. 1(a), on a semiconductor substrate 1,
A photodiode 2 as a photosensitive section that converts incident light into an electric signal and outputs the signal, and bonding pad sections 3 are formed at both ends of each row of the photodiode 2, and on the upper surface thereof, A passivation film 4 is sequentially laminated on the entire upper surface of the passivation film 4 by exposing the bonding pad portion 3, and a filter layer 5 is sequentially laminated on the entire upper surface of the passivation film 4.
The surface 5a is provided with irregularities in accordance with the shape of the microlens 6 to be formed there.

At this time, the protective film of the color film layer 5 covers the bonding pad portion 3, so that the bonding pad portion 3 is not exposed to other acids or the like.

In this state, as shown in FIG. 5B, a photosensitive transparent resist 6a for forming microlenses made of, for example, polystyrene is applied to a thickness of about 2 μm on the upper surface of the filter layer 5, and bonding is performed. The upper part of the pad portion 3 is removed by development.

Then, as shown in the same figure (C), the positive resist 7 is
．． It is coated to a thickness of about 7 μm and patterned into a desired shape so that the positive resist remains at the predetermined position where the microlens 6 is to be formed, that is, above the photodiode 2. In this state, it is exposed to 02 plasma. and dry etching.

By this dry etching, positive resist 7
By gradually removing the resist 6a from above and gradually removing the resist 6a from the exposed portion of the microlens forming resist 6a toward the center of the positive resist, a convex lens-shaped microlens 6 is formed using the resist 6a. At the same time, the resist 6a for forming the microlens is removed from above the peripheral portion 3 to manufacture the solid-state imaging device shown in FIG. 1.

As another method, as shown in FIG. 2(b) above, a silicon-based resist is used as the transparent microlens molding resist 6a, and in addition to this figure, in FIG. A positive resist pattern is also applied to the upper part, and in this state, etching is performed in plasma using Freon gas to form the shape of the upper surface of the microlens 6. Using this half-formed microlens 6 as a mask, 02 By placing it in plasma and performing dry etching, the microlens 6 is completely formed, and the resist above the bonding pad portion 3 of the filter layer 5 is removed, and the solid-state imaging device shown in FIG. 1 is completed. It can also be manufactured.

〔Effect of the invention〕

Since the present invention has the above-described configuration, it is possible to use polystyrene-based or silicon-based resist as the material for the microlens. Not only can this be further improved than a microlens, but it can also reduce the smear phenomenon that causes whitish tails in the top and bottom when photographing bright objects.

Furthermore, there is no reduction in light-receiving sensitivity due to flattening during fixing by resin dripping in a later assembly step, and the heat resistance and light resistance of the filter layer are improved.

In addition, the resist above the bonding pad can be removed by dry etching, which prevents corrosion of the aluminum light-shielding film and prevents development each time, reducing the number of steps and the amount of developer used. reduction can be achieved.

Furthermore, 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 explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the solid-state imaging device according to the present invention, FIG. 2 is a sectional view showing the manufacturing process in order, and FIG. 3 is a sectional view showing a conventional solid-state imaging device. 1... Semiconductor substrate, 2... Photodiode, 3.
...Bonding pad part, 4... Passivation film, 5... Filter layer, 6... Microlens, 6
a...Resist for microlens formation, 7...Positive resist, 6'...Conventional microlens. Applicant's agent Mr. Yu Sato Figure 3 Figure 2

Claims (1)

[Claims] 1. A solid state in which a photosensitive part and a bonding pad part are formed on a semiconductor substrate, the upper surface of this is covered with a filter layer except for the area above the bonding pad part, and a microlens is arranged above the photosensitive part. A solid-state imaging device characterized in that the microlens is formed by dry etching a transparent resist such as silicon-based or polystyrene-based resist. 2. A filter layer is laminated on the upper surface of the semiconductor substrate on which a photosensitive area and a bonding pad area are formed, a transparent resist is applied to this upper surface except above the bonding pad area, and the photosensitive area is formed on top of this resist. Patterning the positive resist located above and performing dry etching to form a microlens with the transparent resist, and using this transparent resist as a mask, remove the resist above the bonding pad portion of the filter layer. A method for manufacturing a solid-state imaging device, characterized by: