JP2000012814A - Solid color imaging element with on-chip lens and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a spectral adjustment for an element easy by so forming as a curvature and a thickness of an on-chip lens to become even per each pixel, by forming a color filter film on the surface and by so fixing the thickness of the color filter as to be a set value for obtaining required spectral characteristics per each color. SOLUTION: A on-chip lens 18 which is provided corresponding to each photo-sensitive element 12 has no color and is transparent and additionally its curvature and a height are constant not relating to different pixel colors. A color filter films 19r, 19g are formed on the on-chip lens 18. A color filter film 19r is a red one and a color filter film 19g is a green one. Film thickness tr, tg and tb of each color filter film 19r, 19g and 19b is not even and the film thicknesses are independently set as their respective required spectral characteristics to be obtained separately. By the means required color representing performance can be obtained and the color representing performance can be easily enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a color solid-state image pickup device with an on-chip lens provided with an on-chip lens for focusing light on a light-receiving element corresponding to each pixel, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A color solid-state imaging device generally has a color filter on which a primary color filter of red, blue, and green or a complementary color filter of cyan, magenta, or the like is appropriately arranged on a substrate surface. In many cases, such a color solid-state imaging device is provided with a lens element (microlens) for increasing the sensitivity of the pixel by condensing the light on the light receiving element for each pixel. FIG. 3 is a schematic sectional view showing one conventional example of such a color solid-state imaging device with an on-chip lens.

In FIG. 1, reference numeral 1 denotes a semiconductor substrate;
.. Are light receiving elements of each pixel, and 3 is a flattening film formed on the surface of the substrate 1 and forms a base of the color filters 4, 4,. Note that a gate insulating film, a transfer electrode, an interlayer insulating film, a light-shielding film, and the like are provided on the substrate 1, and a planarizing film 3 is provided thereon.
These illustrations and descriptions are omitted. Color filters 4, 4, ...
.. forms a transparent resin, to which a dye is added.

An on-chip lens 5 is formed of a transparent resin and has a convex spherical surface, and functions as a convex lens. Therefore, light directed to each pixel from the subject side through the imaging lens can be relatively effectively condensed on the light receiving elements 2, 2,... Of the pixel.

FIGS. 4A to 4E are sectional views showing a method of manufacturing the color solid-state image pickup device with the on-chip lens shown in FIG.

(A) As shown in FIG. 4A, necessary elements such as light-receiving elements 2, 2,..., And vertical registers and horizontal registers not shown in the drawing are formed on the surface of the semiconductor substrate 1, Further, a transfer electrode, an interlayer insulating film, a light-shielding film (Al) and the like are formed on the surface of the substrate 1.

(B) Next, as shown in FIG. 4B, a flattening film 3 is formed. The semiconductor substrate 1 on the surface of the flattening film 3
The height from the surface is, for example, 1.5 to 3 μm.

(C) Next, as shown in FIG. 4C, color filters 4, 4,... Are formed. The color filter 4 is formed by patterning a resin to which a dye or a pigment is added and forming a color filter for one color by repeating a plurality of times for a required color, or once forming a transparent resin entirely, Thereafter, selective dyeing is repeated a plurality of times.

(D) Next, as shown in FIG. 4D, a protective film (thickness, for example, 3 to 4 μm) 6 is applied. The protective film 6 is made of, for example, SOG and has an etching rate substantially equal to that of the transparent resin forming the lens 5.

(E) Next, a transparent resin to be an on-chip lens is formed on the protective film 6, and etching is performed so that the transparent resin is separated from each other independently for each pixel. After that, the surface of each independent transparent resin is subjected to reflow treatment to form on-chip lenses 5, 5,..., As shown in FIG. The height (height from the surface of the protective film) of each of the lenses 5, 5,... Is, for example, 2 to 3 μm.

Then, the lenses 5, 5,... And the protective film 6 are etched back to complete the color solid-state imaging device with the on-chip lens shown in FIG.

By the way, such a conventional color solid-state imaging device with an on-chip lens includes an on-chip lens 5,
Are formed on the color filter 4, the height of the on-chip lens from the surface of the substrate 1 increases, the light cannot be effectively collected on the light receiving element, and it is difficult to sufficiently increase the sensitivity. was there.

That is, a light-shielding film is formed on a transfer electrode formed in a multilayer structure such as two layers or three layers via an interlayer insulating film on the surface of the substrate 1, and a flattening film 3 is further formed on the light-shielding film. , And color filters 4, 4,...
Since the protective film 6 is formed on the color filters 4, 4,..., And the on-chip lenses 5, 5,... Are formed on the protective film 6, the on-chip lenses 5, 5,. The heights of the chip lenses 5, 5,... Are considerably high, so that it is difficult to increase the sensitivity, and condensed light is easily shifted.

Therefore, an attempt was made to form a lens using the color filter itself. That is, the surface of each color filter is made convex spherical so that the function as an on-chip lens is exhibited. However, in the related art, there has been a problem that inconsistency in sensitivity occurs between pixels having different colors.

This is because pixels have different sensitivities for each color due to differences in light transmittance of the color filters and the like, and taking the primary color filters as an example, green has the highest sensitivity, red has the next highest sensitivity, and blue has the highest sensitivity. Is the lowest sensitivity. Therefore, even with the same structure, there was a difference in sensitivity due to the color filters.

Such a difference in sensitivity becomes a factor for reducing the color reproducibility of a picked-up image and is not preferable. Therefore, the applicant of the present application has sought to overcome the problem, and has developed an on-chip lens based on the idea of compensating for the sensitivity difference of the color filter by changing the light-collecting efficiency according to the height of the on-chip lens. Is formed by a color filter, and the height of the on-chip lens of the pixel is made different depending on the sensitivity of the pixel for each color of the color filter, and the invention is disclosed in Japanese Patent Application No. 7-329969.
(Japanese Patent Application Laid-Open No. 9-14854)
No. 9).

According to such a color solid-state image pickup device with an on-chip lens, the color filter and the on-chip lens are not separately formed. Therefore, the height of the on-chip lens is reduced by the thickness of the color filter. Not only can the overall sensitivity be increased,
The manufacturing man-hours can be reduced, and the manufacturing cost can be reduced. In addition, the on-chip lens is used for pixels with low sensitivity according to the difference in sensitivity for each color by the color filter. On the contrary, by setting the height at which the sensitivity becomes low, it is possible to correct the sensitivity difference due to the color filter between the colors of the pixels. In this respect, this is an excellent invention.

[0018]

However, the conventional technique described above (the technique disclosed in Japanese Patent Application Laid-Open No. Hei 148549) has a problem that spectral adjustment cannot be performed. That is, in this prior art, the height and curvature of the lens of each color are different from each other for the purpose of condensing light from the object side as much as possible on the element light receiving portion and for the sensitivity difference between each color due to the difference in color of the color filter. It is decided by itself from the aspect of eliminating lens, and it is impossible to adjust the spectral distribution by the thickness of the lens.

The present invention has been made to solve such a problem, and an object of the present invention is to make it easy to adjust the spectrum of a color solid-state imaging device with an on-chip lens.

[0020]

According to the present invention, an on-chip lens is formed so that the curvature and the thickness are uniform for each pixel, a thin color filter film is formed on the surface thereof, The thickness is set to a value set so as to obtain a desired spectral characteristic for each color.

Therefore, according to the present invention, even if the on-chip lens is formed to have a uniform curvature and thickness, the spectral characteristics can be adjusted by the thickness of the color filter film formed on the surface thereof. Characteristics can be obtained, and in addition, desired color reproduction characteristics can be obtained, and color reproducibility can be easily improved.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color solid-state image pickup device with an on-chip lens according to the present invention is basically a color solid-state image pickup device with an on-chip lens having an on-chip lens corresponding to each pixel and condensing the light on its light receiving element. In the device, the curvature and thickness of the on-chip lens are formed uniformly for each pixel, a thin color filter film is formed on the surface of the on-chip lens, and the thickness of the color filter film is set to a desired value for each color. It is a value set so as to obtain spectral characteristics, and the object of the present invention may be a CCD solid-state imaging device, a MOS solid-state imaging device, or an amplification-type solid-state imaging device. Further, an area sensor type solid-state imaging device or a linear sensor type solid-state imaging device may be used. That is, the present invention can be applied to all color solid-state imaging devices with an on-chip lens.

The on-chip lens may be formed of glass, may be formed of resin, may be formed by a known method, or may be formed by an unknown new method. It doesn't matter. In short, any method may be used as long as the on-chip lens on each pixel can be uniformly formed at a desired curvature and height over all the pixels. Of course, a method used for forming an on-chip lens of a black-and-white solid-state imaging device with an on-chip lens having no color filter film may be used.

The color filter film can be formed on the surface of the on-chip lens by any method as long as it can be formed separately for each color and the thickness of the color filter film for each color can be changed. The point is that the color filter film may be formed for each color so as to have a desired spectral characteristic.For example, the color filter film may be formed by vapor deposition, and the color filter film of each color may be formed according to the amount of vapor deposition. The thickness can be controlled with relatively high precision. Therefore, controllability of spectral characteristics is high, and high color reproducibility can be obtained. The present invention can be applied to a color solid-state imaging device with an on-chip lens regardless of whether it is a primary color filter or a complementary color filter.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 is a sectional view showing one embodiment of a color solid-state imaging device with an on-chip lens according to the present invention. In the drawings, reference numeral 11 denotes a semiconductor substrate, 12, 12,.
, A light-receiving element formed on the surface of the substrate 1, a gate insulating film 13 formed on the surface of the substrate 1, transfer electrodes 14, 14,...
.., Are light receiving elements 12, 1 of the light shielding film 15.
2,... An opening formed in an upper portion, and light from the subject passes through this opening to each of the light receiving elements 12, 12,.
... 17 is a flattening film, 18, 18, ...
.. Are on-chip lenses provided corresponding to the respective light receiving elements 12, 12,..., Which are colorless and transparent, and whose curvature and height are constant irrespective of the color difference of the pixel. . In this regard, the on-chip lens also functions as a color filter, and differs from the technique described in Japanese Patent Application Laid-Open No. 9-148549 in which the curvature and height of the on-chip lens are changed for each color according to the difference in color sensitivity. .

19r, 19g, 19r, 19g,...
Are color filter films formed on the on-chip lenses 18, 18,..., 19r, 19r,... Are red, 19g, 19g,. By the way, in this example, the blue color filter film 19 is used.
, but there are only red and green in the horizontal line shown in FIG. 1, so they do not originally appear in FIG. 1, but a blue color filter film 19b is also shown in the lower right part. . In the next adjacent horizontal line, blue and green color filter films 19b and 19g are alternately arranged.

Then, each of the color filter films 19r, 19
g, 19b is a thickness t _r, t _g, t _b is not uniform, the film thickness setting is made independently for each different as each desired spectral characteristic can be obtained. Therefore, according to such a color solid-state imaging device with an on-chip lens, since the spectral characteristics can be adjusted by the thickness of the color filter film, desired spectral characteristics can be obtained, and further, desired color reproduction characteristics can be obtained. ,
Color reproducibility can be easily increased.

FIGS. 2A to 2C are cross-sectional views showing a main part of a method of manufacturing the color solid-state imaging device with an on-chip lens shown in FIG.

(A) Flat film on solid-state image sensor (Flat film is not necessarily indispensable, and need not be provided.)
The on-chip lenses 18, 18,... Are formed thereon.
The on-chip lenses 18, 18,... Are formed by, for example, a method used for forming on-chip lenses of a black-and-white solid-state imaging device with an on-chip lens having no color filter film. That is, a resist film is formed over the entire surface, a portion of the resist film above each pixel is removed by etching, and thereafter, the resist film is shaped into a dome shape by reflow by heat, and the shape is turned on by an etch-back method or the like. An on-chip lens is formed simultaneously for all pixels by a method such as copying to a chip lens material. Therefore, the film thickness and curvature are constant regardless of the color of the pixel.

Thereafter, a first color filter film, for example, 19r is formed. First, the on-chip lenses 18 other than the on-chip lenses 18 on which the color filter films 19 r are to be formed are masked with the resist film 20. FIG. 2A shows a state after the formation of the resist film 20.

(B) Next, a color, for example, a red dye is vacuum-deposited. 21r is a red dye vapor deposition film. still,
A heat-resistant pigment is used as the pigment. Specifically, the thin and uniform vapor deposition film 21r is formed by heating and sublimating the pigment.
Can be formed. At this time, the film thickness of the color filter film 21r, to a film thickness adjusted to the thickness t _r at which the spectral characteristic is set so as to obtain required to obtain the desired color reproduction. FIG. 2B shows a state at the time of vacuum deposition.

(C) Thereafter, as shown in FIG. 2C, the resist film 20 is removed, and unnecessary portions of the vapor deposition film 21r are removed by lift-off. That is, the color filter film 21r is formed by lift-off.

After that, a second color (for example, green) color filter film 19g is formed by the same method, and after that, a third color (for example, blue) color filter film 19b is formed by the same method. The color solid-state imaging device with an on-chip lens shown in FIG. 1 can be obtained. In this case, what is important is that the color filter film is formed for each color so as to have a desired spectral characteristic.
In the case of a primary color filter, it is necessary to repeat formation of a color filter film three times in red, green, and blue. However, in the case of a complementary color filter, the color filter is not limited to three colors and may be four colors. In some cases, the number of repetitions of the color filter film formation is the same as the number of colors.

[0034]

According to the present invention, even if the on-chip lens is formed to have a uniform curvature and thickness, the spectral characteristics can be adjusted by the thickness of the color filter film formed on the surface thereof. Characteristics can be obtained, and in addition, desired color reproduction characteristics can be obtained, and color reproducibility can be easily improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIGS. 2A to 2C are diagrams illustrating a method of manufacturing a color solid-state imaging device with an on-chip lens according to the first embodiment shown in FIG. FIG. 4 is a cross-sectional view showing a main part of Example 1) in the order of steps.

FIG. 3 is a sectional view showing a conventional example.

FIGS. 4A to 4E are cross-sectional views showing the manufacturing method of the conventional example shown in FIG. 3 in the order of steps.

[Explanation of symbols]

11 ... semiconductor substrate, 12 ... light receiving element, 17 ...
・ Flat film, 18 ・ ・ ・ On-chip lens, 19r, 19
g, 19b ··· color filter _{film, t r, t g, t} b
... The thickness of the color filter film.

Continued on the front page F term (reference) 4M118 AA10 AB01 BA10 BA14 CA02 CA27 CA32 CA40 FA06 FA08 GB11 GC07 GC08 GC09 GD04 GD07 5C024 AA01 CA12 CA31 DA01 EA04 EA08 FA01 GA01 GA51 5C065 BB01 BB42 CC01 DD01 EE10 EE11

Claims (2)

[Claims] 1. A color solid-state imaging device with an on-chip lens provided with an on-chip lens for converging light on a light-receiving element corresponding to each pixel, wherein the curvature and thickness of the on-chip lens are made uniform for each pixel. Forming a thin color filter film on the surface of the on-chip lens, and setting the thickness of the color filter film to a value set to obtain a desired spectral characteristic for each color. Color solid-state image sensor with on-chip lens. 2. An on-chip lens for condensing light on a light-receiving element corresponding to each pixel, wherein the on-chip lens has a curvature,
The thickness is formed uniformly over all the pixels, a thin color filter film is formed on the surface of the on-chip lens, and the thickness of the color filter film is set to a value such that a desired spectral characteristic can be obtained for each color. A method for manufacturing the color solid-state imaging device with the on-chip lens, wherein the on-chip lenses of all pixels are simultaneously formed with the same curvature and thickness regardless of the color of the pixel, and then the surface of the on-chip lens is formed. Forming a thin color filter film having a thickness set so as to obtain a desired spectral characteristic for each color.