JP2000091548A - Solid image pickup element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make feasible of packaging a CCD solid image pickup element formed of a microlens with a light transmissive resin. SOLUTION: A protective film 10 is formed on an N type silicon substrate 1 whereon an isolation regions 3 and N type diffused layer 4 to be a channel region are formed. This protective film 10 contains the first region 11 extending along the isolation regions 3 as well as the second region 12 covering the first regions 11 for flatly forming the surface in the larger refractive index than that in the first regions 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solid-state imaging device having improved light receiving efficiency and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing a configuration of a frame transfer type solid-state imaging device.

The frame transfer type CCD solid-state image pickup device has an image pickup section i, a storage section s, a horizontal transfer section h, and an output section d. The imaging unit i includes a plurality of shift registers extending in the vertical direction and arranged in parallel with each other, and each bit of each shift register forms a light receiving pixel. The accumulation unit s
It consists of a plurality of light-shielded shift registers that are continuous with the shift register of the imaging unit i, and each bit of each shift register constitutes a storage pixel. The horizontal transfer unit h is composed of a single shift register extending in the horizontal direction, and the output of the shift register of the storage unit s is connected to each bit. Output section d
Includes a capacitor that temporarily stores the charge transferred and output from the horizontal transfer unit h and a reset transistor that discharges the charge stored in the capacitor. As a result, the information charges accumulated in each light receiving pixel of the imaging unit i are independently transferred to the accumulation pixels of the accumulation unit s for each pixel, and thereafter, stored in the accumulation unit s row by row.
From the horizontal transfer unit h to the output unit d in pixel units. The output unit d converts the amount of charge for each pixel into a voltage value, and the change in the voltage value is supplied to an external circuit as a CCD output.

FIG. 5 is a plan view showing the structure of the image pickup section i, and FIG. 6 is a sectional view taken along line XX of FIG. These figures show the case where the transfer electrode is a single layer and is driven in three phases.

On one main surface of an N-type silicon substrate 1, a P-type diffusion layer 2 serving as an element region is formed. In the surface region of this P-type diffusion layer 2, isolation regions 3 into which P-type impurities are implanted at a high concentration extend in the vertical direction and are arranged in parallel with each other. An N-type diffusion layer 4 is formed between these isolation regions 3 to form a channel region serving as a transfer path for information charges. A plurality of transfer electrodes 6 made of polycrystalline silicon are arranged in parallel on the N-type diffusion layer 4 with a certain distance therebetween via a gate insulating film 5 made of a thin silicon oxide film. For example, three-phase transfer clocks φ1 to φ3 are applied to these transfer electrodes 6, and the potential state of the channel region is controlled. Then, on the transfer electrode 6, the same interlayer insulating film 7 as the gate insulating film 5 is laminated.

On the interlayer insulating film 7, a semi-cylindrical microlens 8 having a dome-shaped cross section is arranged along the channel region. The micro lens 8 is, for example, a BP
It is formed of SG (Boro-Phospho Silicate Glass) or the like, and condenses light incident on the separation region 3 or the end of the channel region toward the center of the channel region.

In the solid-state image pickup device having the microlenses 8, the light irradiated on the light receiving surface is collected in a region having high light receiving sensitivity and photoelectric conversion is performed, so that the light receiving sensitivity can be improved.

[0008]

In the case where a package of a solid-state imaging device is formed of a translucent resin, the semiconductor substrate 1
The whole will be covered with the translucent resin. As such a package material, an acrylic resin which has good light transmittance, is inexpensive, and has sufficient strength tends to be used.

Since the refractive index of the acrylic resin forming the package is larger than the refractive index of the BPSG forming the microlenses 8, the microlenses 8 do not function properly. That is, since the refractive index is larger in the peripheral region than in the main body of the micro lens 8, the micro lens 8
As shown in FIG. 7, light incident on the channel region spreads from the center of the channel region to both ends, resulting in a reduction in the amount of light incident on the channel region. Therefore, it is difficult to package the element on which the microlenses 8 are formed as it is with the translucent resin.

Accordingly, an object of the present invention is to make a microlens function effectively while directly packaging with a translucent resin.

[0011]

According to the present invention, there is provided a solid-state imaging device comprising: a semiconductor substrate; a plurality of light receiving pixels arranged on a principal surface of the semiconductor substrate with a predetermined gap therebetween; A light-transmitting protective film that is stacked on one main surface of the semiconductor substrate so as to cover the semiconductor substrate, wherein the protective film covers at least a gap between the plurality of light-receiving pixels, and the arrangement of the plurality of light-receiving pixels. A first region having a semi-cylindrical shape extending along the first region, a second region covering the first region, having a flat surface, and having a larger refractive index than the first region; It is characterized by including.

In the method of manufacturing a solid-state imaging device according to the present invention, a plurality of light-receiving pixels are arranged on one main surface of a semiconductor substrate with a predetermined gap therebetween, and the plurality of light-receiving pixels are formed on the semiconductor substrate. Along the gap between the light receiving pixels, the first
Forming a resin pattern by laminating the resin, heating the resin pattern to make it viscous flow, forming a semi-cylindrical shape covering the gap between the plurality of light receiving pixels, and forming a semi-cylindrical shape on the semiconductor substrate. Covering the first resin and flattening the surface and laminating the first resin, dissolving the first resin in the second resin, and corresponding to the first resin in the second resin. Forming a cavity to be formed.

According to the present invention, the concave lens is formed in the gap between the plurality of light receiving pixels, and the light incident on the gap is scattered toward the channel region, so that the amount of light incident on the channel region increases. Further, since the surface of the protective film is formed to be flat, the protective film can be packaged by contacting the transparent resin.

[0014]

FIG. 1 is a sectional view showing a first embodiment of a solid-state imaging device according to the present invention, and shows the same portions as FIG.

N-type silicon substrate 1, P-type diffusion layer 2, isolation region 3, N-type diffusion layer 4, gate insulating film 5, transfer electrode 6
The interlayer insulating film 7 is the same as the solid-state imaging device shown in FIG. The feature of the present invention resides in that the first region 11 functioning equivalently to the micro lens is formed on the interlayer insulating film 7.
And a translucent protective film 10 including the second region 12.

The first region 11 in the protective film 10 has a semi-cylindrical shape having a dome-shaped cross section, and is disposed on the separation region 3 so as to straddle between adjacent channel regions. It extends along the region 3. In this embodiment, the first region 11 is formed in a cavity. And
The second region 12 of the protective film 10 covers the entire first region 11 and is formed with a flat surface. In this embodiment, the second region 12 is formed of an acrylic resin transparent to visible light. Usually, since the refractive index of the acrylic resin is higher than the refractive index in the air, the first region 11
Functions as a concave lens in the protective film 10. Therefore,
Light incident on the separation region 3 is refracted toward the channel region at the interface between the first region 11 and the second region 12 as shown in FIG. Led to.

In such a solid-state imaging device, the surface of the protective film 10 is formed flat, so that the package and the protective film 10 can be formed using any kind of translucent resin. Light is no longer refracted at the interface in unwanted directions. Further, since the first region 11 covered by the second region 12 in the protective film 10 functions as a lens, the function of the lens is not affected by the material of the package.

FIG. 2 is a sectional view showing a second embodiment of the solid-state imaging device of the present invention. This figure also shows the same parts as in FIG. 6, as in FIG.

The second embodiment differs from the first embodiment in that the first region 11 'of the protective film 10' is formed of a material having a lower refractive index than the second region 12. is there. That is, the first region 11 'is formed using a material having a lower refractive index than acrylic resin such as BPSG, and the first region 11' is covered with the second region 12 made of acrylic resin. The protection film 10 'is formed. Also in this protective film 10 ', as in FIG.
The light incident on the separation region 3 is divided into the first region 11 ′ and the second region 11 ′.
Is refracted toward the channel region at the interface with the region 12.

FIGS. 3A to 3D are cross-sectional views for explaining steps of a method for manufacturing a solid-state image sensor according to the present invention. In this figure, the same parts as those in FIG. 1 are shown. (A): First Step A P-type impurity such as boron is diffused in a surface region of an N-type silicon substrate 1 to form a P-type diffusion layer 2 serving as an element region. A plurality of isolation regions 3 are formed by selectively implanting a P-type impurity into the P-type diffusion layer 2. An N-type impurity such as phosphorus is implanted between the isolation regions 3 to form a channel. A P-type diffusion layer 4 serving as a region is formed. Subsequently, the surface of the silicon substrate 11 on which the P-type diffusion layer 4 is formed is thermally oxidized,
A gate insulating film 5 made of silicon oxide is formed. Then, a plurality of transfer electrodes 6 made of polycrystalline silicon are formed on the gate insulating film 5, and an interlayer insulating film 7 is formed to cover the transfer electrodes 6.

This first process is the same as the well-known manufacturing process for manufacturing the conventional solid-state imaging device shown in FIG.

(B): Second Step A heat-softening resin layer 15 containing wax as a main component is formed on the interlayer insulating film 7, and the resin layer 15 is patterned along the isolation region 3. A rectangular pattern 16 is formed. The rectangular pattern 16 is formed on the separation region 3 so as to straddle between the channel regions on both sides, and extends along the separation region 3.

(C): Third Step A semi-cylindrical pattern 17 is formed by heating the rectangular pattern 16 and causing it to viscously flow. The shape of the first region 11 of the protective film 10 is determined by the semi-cylindrical pattern 17.

(D): Fourth step An acrylic resin is applied on the silicon substrate 1 on which the semi-cylindrical pattern 17 is formed, and the semi-cylindrical pattern 17 is completely covered. Then, the protective film 10 is formed by heating at a temperature at which the resin constituting the semi-cylindrical pattern 17 is melted and the acrylic resin is cured. At this time, by selecting the material of the semi-cylindrical pattern 17 (rectangular pattern 16) to be melted into the acrylic resin, a space corresponding to the semi-cylindrical pattern 17 is formed after the acrylic resin is cured. This space forms the first region 11, and the cured acrylic resin forms the second region.

According to the above-described manufacturing method, a solid-state imaging device having the protective film 10 shown in FIG. 1 can be obtained.

In this embodiment, the application of the frame transfer method to the solid-state imaging device has been exemplified. However, the solid-state image sensor of the interline transfer method or the frame interline transfer method in which a vertical transfer register is arranged between light receiving pixels. Application to an imaging device, and further application to a MOS type solid-state imaging device are also possible. In the case of these solid-state imaging devices, the separation region extends in both the vertical and horizontal directions,
The first region 11 of 0 is formed in a mesh shape along the separation region, has a semi-cylindrical shape other than the intersection, and is configured to function as a concave lens. When a vertical transfer register or the like is formed along the separation region, the first region 11 of the protective film 10 is formed so as to cover the vertical transfer register together with the separation region.

[0027]

According to the present invention, the light irradiated to the separation region (the region where photoelectric conversion is not performed) is refracted in the protective film so as to go to the adjacent photoelectric conversion region side. Most of the light incident on the light receiving surface is used for photoelectric conversion. At this time, since the surface of the protective film is formed flat, even if a light-transmitting resin package is formed in contact with the protective film, unnecessary refraction occurs at the interface between the protective film and the light-transmitting resin. Will not occur. Further, the first region of the protective film functioning as a lens has a second region.
No matter what material is laminated on the protective film, the function is not lost. Therefore, it is possible to form a package using a light-transmitting resin without being limited by a material, while forming a light-collecting microlens on the surface of the element.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a solid-state imaging device according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the solid-state imaging device of the present invention.

FIG. 3 is a cross-sectional view for explaining a method of manufacturing a solid-state imaging device according to the present invention in each step.

FIG. 4 is a schematic diagram illustrating a configuration of a frame transfer type solid-state imaging device.

FIG. 5 is a plan view illustrating a structure of an imaging unit of a conventional solid-state imaging device.

FIG. 6 is a sectional view showing a sectional structure taken along line XX of FIG. 5;

FIG. 7 is a cross-sectional view showing how light is refracted in a conventional solid-state imaging device.

[Explanation of symbols]

 i Imaging unit s Storage unit h Horizontal transfer unit d Output unit 1 Silicon substrate 2 P-type diffusion layer 3 Isolation region 4 N-type diffusion layer 5 Gate insulating film 6 Transfer electrode 7 Interlayer insulating film 10, 10 'Protective film 11, 11' 1st area 12 2nd area 15 Resin layer 16 Rectangular pattern 17 Semi-cylindrical pattern

Claims (3)

[Claims] A semiconductor substrate; a plurality of light receiving pixels arranged on the one main surface of the semiconductor substrate with a predetermined gap therebetween; and a plurality of light receiving pixels on the one main surface of the semiconductor substrate covering the plurality of light receiving pixels. A light-transmitting protective film that is laminated, wherein the protective film covers at least a gap between the plurality of light receiving pixels, and has a semi-cylindrical first shape extending along the arrangement of the plurality of light receiving pixels. And a second region having a flat surface covering the first region and having a larger refractive index than the first region. 2. The solid-state imaging device according to claim 1, wherein the second region of the protective film is made of a light-transmitting resin, and the first region of the protective film is hollow. 3. A step of arranging a plurality of light receiving pixels on one main surface of a semiconductor substrate with a predetermined gap therebetween, and forming a plurality of light receiving pixels on the semiconductor substrate along a gap between the plurality of light receiving pixels. Laminating a first resin to form a resin pattern, heating the resin pattern to cause a viscous flow, and forming a semi-cylindrical shape covering a gap between the plurality of light receiving pixels;
A step of covering the semi-cylindrical first resin on the semiconductor substrate, flattening the surface, and laminating the first resin; dissolving the first resin in the second resin; Forming a cavity corresponding to the first resin.