JPH06302793A - Solid-state image sensing device and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a solid-state image sensing device with a micro-lens having the reliability of heat resistance, chemical resistance, etc., and resulting in no fluctuation of spectral sensitivity due to the reduction of transmittance and manufacture thereof. CONSTITUTION:An inter-insulating-layer film 31 is formed onto a solid-state image sensing device with a light-receiving section 2 and a signal reading section, and a lens layer 32 is shaped onto the film 31 through the plasma CVD method on SiO2. A lens clearance section 33 and a convex-shaped lens layer 32 are formed through isotropic etching, and the convex-shaped lens layer 32 is polished through a chemical-mechanical polishing method, thus forming a lens-shaped section 34. The surface of the lens-shaped section 34 is rinsed to shape a lens surface 35, and an antireflection film 36 is formed, thus constituting a micro-lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device having a microlens and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, a solid-state image pickup device such as a CCD or a MOS imager has a light receiving portion for converting incident light into an electric signal and a signal reading portion for transferring a signal generated in the light receiving portion on the same semiconductor substrate. is doing. 5A and 5B
FIG. 4A is a pixel cross-sectional view and a plan view of a conventional MOS solid-state imaging device. In the figure, 1 is a semiconductor substrate, 2 is a light receiving portion, 3
Is an n ⁺ diffusion region, 4 is a gate electrode, 5 is a gate oxide film,
6 is a p ⁺ diffusion region, 7 and 8 are insulating interlayer films, 9 is a metal wiring, 10 is a field oxide film, 11 is a contact hole, 12
Indicates incident light, respectively.

By the way, the MO configured as described above
In the S-type solid-state imaging device, the area ratio (aperture ratio) of the light receiving portion 2 where the incident light 12 is actually photoelectrically converted, out of the area of the entire region where the light is incident, is 10 to 10
It has the drawback of being limited to about 50%.

As a means for compensating for this aperture ratio, for example, a microlens laminated structure disclosed in Japanese Patent Publication No. 60-97552 is known. FIG. 6 is a diagram showing a pixel cross section of a conventional solid-state imaging device including a microlens. In this configuration example, a transparent insulating interlayer film 14 is formed on the surface of an image sensor, and a microlens layer for condensing light incident on the light receiving portion 2 and its peripheral portion on the light receiving portion 2 on the interlayer film 14. 13 is formed, and with this configuration, the output of the solid-state imaging device is 10% compared to the conventional example in which the microlens layer is not formed.
~ 500% expected to improve.

[0005]

However, the conventional method of forming a microlens layer is mainly a flowing method by thermal softening. Therefore, it is difficult for the solid-state imaging device after forming the microlens layer to have heat resistance equal to or higher than the softening point of the material for forming the microlens layer. There was a problem that was limited. In addition, depending on the material of the microlens layer, due to deterioration due to chemicals or gas,
Further, there is a drawback that the transmittance deteriorates due to the material itself.

The present invention has been made in order to solve the above-mentioned problems in the conventional solid-state image pickup device having a microlens, and has the reliability such as heat resistance and chemical resistance as those of conventional semiconductor devices. Another object of the present invention is to provide a solid-state imaging device including a microlens that does not change the spectral sensitivity by reducing the transmittance and a manufacturing method thereof.

[0007]

In order to solve the above-mentioned problems, the present invention provides a solid-state image pickup device having a plurality of photoelectric conversion elements arranged in a matrix on a semiconductor substrate. A microlens made of a transparent insulating film that collects incident light and is stable in heat resistance and chemical resistance is provided in a portion corresponding to the light receiving portion.

In the solid-state image pickup device having such a structure, the microlenses are formed of an insulating film having excellent heat resistance and chemical resistance. Therefore, even after the microlenses are formed, a semiconductor process such as heating lamination or etching is performed. It is possible to perform the above, and the use range of the solid-state imaging device is not limited.
Further, it is possible to suppress the fluctuation of the spectral sensitivity without reducing the transmittance.

Further, in the method for manufacturing a solid-state image pickup device according to the present invention, the microlenses made of an insulating film are formed by polishing the insulating film by a chemical-mechanical polishing method.

The chemical-mechanical polishing method refers to "Solid state te
ch / Japan version, July, 1992, pp32-37 ", etc., which is one of the semiconductor planarization methods and is being used mainly for DRAMs and the like. Chemical-mechanical polishing is shown in FIG. The chemical-mechanical polishing method is used for the projection 21 of the insulating interlayer film.
The purpose is to completely flatten the surface of the concave portion 22 by polishing it. Therefore, (A) of FIG.
As shown in, a hard polishing pad (hard polishing) is used in order to concentrate the pressure on the upper surface of the convex portion 21 of the insulating interlayer film and advance the polishing in the vertical direction 23. In this case, in order to secure the polishing uniformity between chips in the wafer surface, it is necessary to take measures such as adjusting the polishing interface of the polishing pad to the contour of the wafer. In FIG. 1 (A), 24 is the polishing lateral pressure,
The numeral 25 indicates the pressure applied to the end of the convex portion. By performing such polishing, as shown in FIG.
21 is ground into a shape 21a. In addition, in FIG. 1B, a indicates a height before polishing, b indicates a height after polishing, and c indicates a height serving as a bottom.

On the other hand, when a relatively soft polishing pad (soft polishing) is used, as shown in FIG. 2A, the polishing pressure is dispersed in the horizontal direction in the convex portion 21 of the insulating interlayer film, The polishing lateral pressure 24 becomes large, and the pressure 25 is intensively applied in the oblique direction near the end of the convex portion 21.
For this reason, the polishing is insufficient for polishing for flattening, but since the pressure applied to the entire wafer surface is dispersed, the wafer surface is likely to be uniformly polished. Therefore, as the soft polishing proceeds, the shape of the convex portion 21 will be polished into a spherical shape as indicated by 26, as shown in FIG. 2B. Therefore, by using this soft polishing method for forming a microlens and appropriately setting the hardness to be polished, the polishing agent, the polishing rotation speed, etc., a microlens having an arbitrary lens ratio can be formed.

Therefore, depending on the polishing conditions, for example, SiO 2
_Since it becomes possible to polish a material such as ₂ to form a lens, it is possible to form a microlens using a material having stable heat resistance and chemical resistance.

[0013]

EXAMPLES Next, examples will be described. 3A to 3F are manufacturing process diagrams for explaining one embodiment of a solid-state imaging device including a microlens according to the present invention and a manufacturing method thereof. First, as shown in FIG. 3A, a MOS type solid-state imaging device having the same configuration as that of the conventional example shown in FIG. Since this manufacturing process is a general process, its description is omitted, and the same parts as those in FIG. In this embodiment, the MOS
Although the present invention is applied to a solid-state image pickup device, any solid-state image pickup device using photoelectric conversion elements such as CCD, AMI, SIT, and CMD can be applied.

Next, as shown in FIG.
Using the on-glass method, for example, OCDTYPE-7 (manufactured by Tokyo Ohka Co., Ltd.) is spin coated to form the insulating interlayer film 31. In addition to the usual CVD method and sputtering method, TEOS-CVD method, bias sputtering method, the above spin-on-glass method, etc. may be used alone or by any of these as a method of forming this insulating interlayer film 31. A combination of methods may be used. The insulating interlayer film 31 may be made of any material as long as it transmits light and has mechanical strength. For example, SiO _X (0 <X ≦
2), SiN _Y (0 <Y ≦ 1.3), SiC _Z (0 <Z ≦ 1)
And so on.

Next, as shown in FIG. 3C, a lens layer 32 is formed on the insulating interlayer film 31 by a plasma CVD method of SiO ₂ . The lens layer 32 may be made of the same material and the same forming method as the insulating interlayer film 31, or may be formed of the insulating interlayer film 31 itself. Then, after forming a pattern in which the lens gap is opened with a resist or the like, isotropic etching such as wet etching or CDE is performed to remove the lens layer 32 in the lens gap 33 and to form the outer shape of the lens shape. Then, a convex lens layer 32 is formed.
Also in this case, for example, the convex shape may be formed by anisotropic etching such as RIE or a lift-off method. Next, as shown in FIG. 3D, the convex lens layer 32 is polished by using a chemical-mechanical polishing method to form a lens-shaped portion 34.

Next, a polishing apparatus for chemical-mechanical polishing will be described with reference to FIG. First, the wafer to be polished
Fixing base made of glass or stainless steel with polishing side facing up
Fix to 40 with fixative 41. After that, a polishing pad 43 made of a cloth such as cotton filled with a slurry (viscous) polishing liquid 42 containing TiO ₂ or the like is pressed against the wafer 44 and the polishing table 40, and the polishing pad 43 or the wafer 44, or both of them are pressed. The surface of the wafer 44 is polished by rotating the polishing rotating plate 45. At this time, in order to achieve soft polishing, the polishing rotation speed is 1000 rotations /
Not more than a minute. As the slurry particles, those oxides based CeO _2, SiO ₂ or the like in addition to TiO ₂ and, SiC, may be C or the like. Further, the polishing pad 43 may be made of polyurethane other than cloth. The convex shape on the surface of the wafer 44 is formed into a lens shape by these arbitrary polishing slurries and the rotation speed.

Next, as shown in FIG. 3E, after polishing, the wafer is cleaned by washing with water, showering, scrubbing, ultrasonic cleaning, etc., and the surface layer of the lens-shaped portion 34 is further cleaned with an HF diluted aqueous solution. Rinse. In FIG. 3E, reference numeral 35 indicates the lens surface after rinsing. Finally, as shown in FIG. 3F, an antireflection film 36 of MgF or the like is formed on the lens surface 35 to complete a solid-state imaging device provided with microlenses.

As described above, in the present invention, since the microlens is formed of a thermally and mechanically stable material, for example, when the antireflection film 36 and the inorganic color filter are laminated and processed, It is possible to form a material that requires a heating process.

[0019]

As described above on the basis of the embodiments,
According to the present invention, it has reliability such as heat resistance and chemical resistance,
Further, it is possible to realize a solid-state imaging device including a microlens that does not cause a change in spectral sensitivity due to a reduction in transmittance. Further, according to the manufacturing method of the present invention, a microlens can be easily formed using a material having stable heat resistance and chemical resistance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining the concept of a chemical-mechanical polishing method.

FIG. 2 is an explanatory diagram for explaining the concept of soft polishing in chemical-mechanical polishing.

FIG. 3 is a manufacturing process diagram for explaining an embodiment of the solid-state imaging device and the manufacturing method thereof according to the present invention.

FIG. 4 is a diagram showing a configuration example of a chemical-mechanical polishing device.

5A and 5B are a cross-sectional view and a plan view showing a configuration example of a conventional MOS solid-state imaging device.

FIG. 6 is a cross-sectional view showing a configuration example of a conventional MOS solid-state imaging device including a microlens.

[Explanation of symbols]

1 semiconductor substrate 2 light receiving part 3 n ⁺ diffusion region 4 gate electrode 5 gate oxide film 6 p ⁺ diffusion region 7, 8 insulating interlayer film 9 metal wiring 10 field oxide film 31 insulating interlayer film 32 lens layer 33 lens gap 34 lens shape Part 35 Lens surface 36 Anti-reflection film

Claims (4)

[Claims] 1. A solid-state image pickup device comprising a plurality of photoelectric conversion elements arranged in a matrix on a semiconductor substrate, wherein incident light is condensed at a portion corresponding to a light receiving portion of the photoelectric conversion element, and heat resistance and A solid-state image pickup device comprising microlenses each formed of a transparent insulating film having stable chemical resistance. 2. The insulating film is formed of SiO _x (0 <X ≦ 2),
2. The solid-state image pickup device according to claim 1, wherein the solid-state image pickup device is composed of either SiN _Y (0 <Y ≦ 1.3) or SiC _Z (0 <Z ≦ 1). 3. A micro insulating film comprising a transparent insulating film which collects incident light at a portion corresponding to a light receiving portion of a plurality of photoelectric conversion elements arranged in a matrix on a semiconductor substrate and which is stable in heat resistance and chemical resistance. In the method of manufacturing a solid-state imaging device, each of which forms a lens, the microlens made of the insulating film is formed by polishing the insulating film by a chemical-mechanical polishing method. 4. The method for manufacturing a solid-state imaging device according to claim 3, wherein the chemical-mechanical polishing method is incomplete planarization polishing using a soft polishing pad.