JP2737946B2 - Method for manufacturing solid-state imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid-state imaging device, and more particularly, to a method for manufacturing a solid-state imaging device having a condensing lens for each pixel. It is.

[Summary of the Invention] The present invention relates to a method of manufacturing a solid-state imaging device including a lens that collects light for each pixel of a light-receiving section of a solid-state imaging device. A layer having an opening is formed thereon, and then an interlayer insulating film is formed in the opening so that the surface of the interlayer insulating film is depressed toward the light receiving portion, and the interlayer insulating film is solidified by heat treatment. After that, a film having a higher refractive index than the interlayer insulating film is laminated on the interlayer insulating film, and a lens having good light-collecting efficiency is provided by forming a lens in the recess of the interlayer insulating film. This makes it possible to easily obtain a solid-state imaging device.

[Related Art] In recent years, in a solid-state imaging device, the total number of pixels of the solid-state imaging device has increased with the increase in integration, and an increase in a wiring layer area ratio and a reduction in a light receiving area have been inevitable. For this reason, there has been a problem that the amount of light to the light receiving portion of the element decreases, and the sensitivity of the solid-state imaging device decreases. Therefore, as a means for preventing such a decrease in sensitivity, a method has been considered in which a condenser lens for increasing the light amount of each element is formed on-chip. A method of manufacturing this type of solid-state imaging device is disclosed in Japanese Patent Application Laid-Open No. 62-23161.
This is disclosed in Japanese Patent Application Publication No.

 2A to 2I show this manufacturing method.

First, as shown in FIG. 2A, a silicon oxide film 3 is formed on a silicon substrate 1 on which a light receiving section 2 is formed (see FIG. 2A).
Figure B). Next, as shown in FIG. 2C, a polysilicon film 4 is deposited on the silicon oxide film 3. Then, as shown in FIG. 2D, after a thin silicon oxide film 5 is formed on the polysilicon film 4, a silicon nitride film 6 is deposited by an LPCDV method or the like as shown in FIG. Patterning is performed so as to cover portions other than 2. Next, as shown in FIG. 2F, when oxidation is performed, the polysilicon film 4 below the silicon nitride film 6 is not oxidized, and only the portion not covered with the silicon nitride film 4 is oxidized to form a silicon nitride film. An end portion covered by 6 becomes a bird's beak 7. Next, as shown in FIG. 2G, the silicon nitride film 4 and the upper silicon oxide film 5 (including the bird's beak 7) are removed. Next, the second
As shown in FIG. H, the polysilicon film 4 is oxidized, and thereafter, as shown in FIG.
If a silicon nitride film 8 is deposited by an LPCVD method or the like and the surface is flattened by an etch-back method or the like, a lens portion A is formed on the silicon nitride film 8.

[Problem to be Solved by the Invention] However, in such a conventional method for manufacturing a solid-state imaging device, since the surface of the silicon oxide film 3 after removing the bird's beak 7 is flat, the lens portion A is There is a problem that the shape has a radius only at the peripheral edge and the light collection efficiency is poor.

Further, the conventional manufacturing method has a problem that the number of steps is increased and the cost is increased.

The present invention has been made in view of such conventional problems, and has as its object to obtain a solid-state imaging device provided with a lens having high light-collecting efficiency.

Means for Solving the Problems Accordingly, the present invention provides a method for manufacturing a solid-state imaging device including a lens that collects light for each pixel of the light-receiving unit of the solid-state imaging device, wherein the light-receiving unit is formed. Forming a layer having an opening on the light receiving portion on the substrate, and then forming an interlayer insulating film in the opening so that the surface of the interlayer insulating film is depressed toward the light receiving portion; The solution is to solidify the insulating film by heat treatment, stack a film having a higher refractive index than the interlayer insulating film on the interlayer insulating film, and form a lens in the recess of the interlayer insulating film. Means.

[Operation] Since the film formed in the recess of the interlayer insulating film has a higher refractive index than the interlayer insulating film, it condenses the light to the light receiving section and increases the light amount of the solid-state imaging device to improve the sensitivity.

Embodiment Hereinafter, details of a method for manufacturing a solid-state imaging device according to the present invention will be described based on an embodiment shown in the drawings.

First, as shown in FIG. 1A, after forming a light receiving portion 11 as a photodiode on a silicon substrate 10, a silicon oxide film (or SiN film) 12 is formed by a CVD method (FIG. 1B).

Next, a glass layer 13 is formed on the silicon oxide film 12, and an opening 14 is opened in the glass layer 13 on the light receiving section 11. The inner wall of the opening 14 is formed to have a predetermined inclination (FIG. 1C).

Further, the opening 14 and the glass layer 12 thus formed are formed.
For example, as shown in FIG. 1D, for example, an SOG (coated glass) 15 which is an interlayer insulating film is applied. At this time, opening 14
The inner SOG 15 has a concave shape whose center is the most depressed due to surface tension. Next, annealing is performed to solidify the SOG 15.

Next, on the SOG 15 thus formed, for example, a SiN (silicon nitride) film 16 having a higher refractive index than the SOG is formed by a CVD method (FIG. 1E).

Finally, as shown in FIG. 1F, the lens portion A is formed by flattening the SiN film 16.

Although the embodiment has been described above, various other design changes are possible. For example, in the above embodiment,
Although the glass layer 13 is provided on the silicon oxide film 12, a layer made of another material may be used. In the above embodiment, the opening of the glass layer 13 was
Although the inner wall 14 has a tapered shape, an opening perpendicular to the lower oxide film 12 may of course be used. In order to adjust the degree of curvature of the concave shape of the SOG, the inclination of the inner wall of the opening 14 can be set in advance.
It is possible to design the slope according to the structure.

Further, in the above embodiment, the SiN film is used as the film having a higher refractive index than SOG, but other materials may be used.

[Effects of the Invention] As is apparent from the above description, in the method for manufacturing a solid-state imaging device according to the present invention, a lens portion is formed by combining an interlayer insulating film and a substance having a higher refractive index than the interlayer insulating film. As a result, the lens can be easily formed (because the curvature due to the surface tension of the interlayer insulating film can be used), and the cost can be reduced.

Further, even if there is some distortion, effective light collection can be performed on the light receiving section, so that the amount of light per pixel can be increased, and the sensitivity of the solid-state imaging device can be increased.

[Brief description of the drawings]

1A to 1F are cross-sectional views showing an embodiment of a method for manufacturing a solid-state imaging device according to the present invention, and FIGS. 2A to 2I are cross-sectional views showing a conventional example. A: lens section, 10: silicon substrate, 11: light receiving section,
13 ... glass layer, 14 ... aperture, 15 ... SOG, 16 ... SiN
film.

Claims (1)

(57) [Claims] 1. A method for manufacturing a solid-state imaging device comprising a lens for condensing light for each pixel of a light-receiving portion of a solid-state imaging device, wherein a hole is formed in the light-receiving portion on a substrate on which the light-receiving portion is formed. Then, an interlayer insulating film is formed in the opening so that the surface of the interlayer insulating film is depressed toward the light receiving portion, and the interlayer insulating film is solidified by heat treatment. A method for manufacturing a solid-state imaging device, comprising: laminating a film having a higher refractive index than the interlayer insulating film on the interlayer insulating film; and forming a lens in the recess of the interlayer insulating film.