JPH10209420A - Manufacture of solid-state imaging element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve such imaging characteristics as color-sensitive-ratio, color tone, etc., by using a mask comprising such a pattern part as different in size according to thickness of an on-chip color filter for each pixel, for lithography to a material layer of an on-chip lens. SOLUTION: As a material layer of an on-chip lens, a photo-resist 35 is applied on a flattened film 34. Then, with a mask 36 where such pattern part 36a as on a pixel where only a red filter 33a, a blue filter 33b, or a yellow filter 33c is formed has the same size d1 as a prior art, while such a pattern part 36b as on the pixel where a green filter is formed with the yellow filter 33c laminated on the blue filter 33b has a size d6 smaller than a prior art, the photo-resist 35 is exposed. Since pattern parts 36a and 36b of a mask 36 have different sizes d1 and d6 during development, halation effect, etc., at the photo resists 35 are corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid-state image pickup device having an on-chip color filter and an on-chip lens on the color filter in each pixel.

[0002]

2. Description of the Related Art FIGS. 5 to 7 show a conventional example of the present invention for manufacturing a CCD type solid-state image pickup device having a complementary color system on-chip color filter. In this conventional example, as shown in FIG. 5, a p-well 12 is formed in a Si substrate 11, and a p-region 13 and a n-region 13 are formed as hole accumulation regions closer to the surface of the Si substrate 11 than the p-well 12. The sensor 15 is formed by forming the region 14.

[0003] A p-region 16 as a readout portion is formed on the side of the sensor 15, and an n-region 17 as a vertical transfer portion is formed on the side of the p-region 16. In addition, a p-well 21 is formed below the n-region 17, and a p-region 22 as a pixel separation portion is formed beside the n-region 17. Then, an SiO ₂ film 23 as a gate insulating film is formed on the surface of the Si
A transfer electrode is formed from the polycrystalline Si film 24 on the i-substrate 11.

Then, the polycrystalline Si film 24 is covered with an SiO ₂ film 25 or the like as an insulating film, and the Si substrate 11 and the SiO ₂ film 25 are covered with a SiO ₂ film 26 as a passivation film. Then, the light shielding film 27 such as an Al film or a W film is
₂ Opening 27 a formed on film 26 and corresponding to sensor 15
Is provided on the light shielding film 27.

Then, a passivation film SiN is formed.
The light-shielding film 27 and the like are covered with the film 31, and a planarization film 32 is formed on the SiN film 31. Then, as shown in FIGS. 4A to 4C, the red filter 33a, the blue filter 33b, and the yellow filter 33c are sequentially patterned on the flattening film 32, and as shown in FIG. Next, a checkered on-chip color filter 33 corresponding to each pixel is formed.

Since the on-chip color filter 33 is a complementary color system, a green filter is formed by laminating a blue filter 33b and a yellow filter 33c. After that, a flattening film 34 is formed on the on-chip color filter 33, and a positive photoresist 35 as a material layer of the on-chip lens is applied on the flattening film 34.

Then, the photoresist 35 is exposed using a mask 36 having pattern portions 36a and 36b corresponding to the on-chip lenses to be formed. Next, FIG.
As shown in FIG. 7, the photoresist 35 is developed to form pattern portions 35a and 35b on each pixel, and as shown in FIG.
The pattern portions 35a and 35b are reflowed to form the on-chip lenses 37a and 37b.

[0008]

By the way, as is apparent from FIG. 5, the on-chip color filter 33 has a greater effect than a portion where only one of the red filter 33a, the blue filter 33b and the yellow filter 33c is formed. The portion where the green filter is formed by laminating the yellow filter 33c on the blue filter 33b is thicker, and the thickness of the on-chip color filter 33 is not uniform.

On the other hand, if the height from the surface of the Si substrate 11 to the on-chip lenses 37a and 37b is high, it is not easy to control the focal points of the on-chip lenses 37a and 37b near the sensor 15, and the sensitivity is high. Decrease.

For this reason, as shown in FIG. 5, the flattening film 34 on the on-chip color filter 33 cannot be made sufficiently thick, and the surface of the flattening film 34 is made sufficiently flat. Can not do. Therefore, the photoresist 3
At the time of exposure 5, halation or the like occurs due to reflection of light at the step portion of the flattening film 34.

Nevertheless, in the above-described conventional example, since the mask 36 has the pattern portions 36a and 36b of the same size d ₁ on any of the pixels, as shown in FIG. , after development of the photoresist 35, the red filter 33a, the size d ₂ of the pattern portion 35a on the pixels forming only one of the blue filter 33b or yellow filter 33c is stacked yellow filter 33c on the blue filter 33b The pattern portion 35 on the pixel on which the green filter is formed
It is smaller than b size d _3.

For this reason, as shown in FIG. 7, the size d ₄ of the on-chip lens 37a on the pixel on which only one of the red filter 33a, the blue filter 33b and the yellow filter 33c is formed forms a green filter. It was smaller than the size d ₅ of the on-chip lens 37b on the pixel. Accordingly, in this CCD type solid-state imaging device, the sensitivity of green is higher than the sensitivity of other colors. In the conventional example shown in FIGS. It was difficult to manufacture the device.

[0013]

According to the present invention, there is provided a method for manufacturing a solid-state image sensor, wherein each pixel includes an on-chip color filter and an on-chip lens in an upper layer thereof. Lithography is performed on the material layer of the on-chip lens using a mask having a pattern portion having a size different according to the thickness of the on-chip color filter.

In the method of manufacturing a solid-state imaging device according to the present invention, a positive photoresist is used as the material layer,
The pattern portion having a relatively small size may correspond to the on-chip color filter having a relatively large thickness.

In the method of manufacturing a solid-state imaging device according to the present invention, the on-chip color filter having a laminated structure may be formed.

In the method of manufacturing a solid-state imaging device according to the present invention, the on-chip color filter having a single-layer structure may be formed.

In the method of manufacturing a solid-state imaging device according to the present invention, a material layer of an on-chip lens is formed by using a mask having a pattern portion having a size different depending on the thickness of an on-chip color filter for each pixel. Since the lithography is performed on, the halation effect and the like in this material layer can be corrected even if the base of the material layer of the on-chip lens is not flat because the thickness of the on-chip color filter is not uniform, The shape of the on-chip lens of any pixel can be made uniform.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to the manufacture of a CCD type solid-state imaging device having a complementary color-based on-chip color filter will be described below with reference to FIGS. Also in this embodiment, as shown in FIG. 1, a positive photoresist 35 as a material layer of an on-chip lens is used.
Until is applied on the flattening film 34, substantially the same steps as those of the above-described conventional example are performed.

However, in this embodiment, the red filter 33a, the blue filter 33b or the yellow filter 33c
The pattern portion 36a on the pixel in which only _one of them is formed has the same size d1 as in the conventional example, but the blue filter 3
On 3b by laminating the yellow filter 33c pattern portion 36b on the pixel forming a green filter using a mask 36 which has a smaller size d ₆ than a conventional example, exposing the photoresist 35.

More specifically, in the case of a CCD type solid-state imaging device having 380,000 pixels using a 1/4 inch optical system, the size of a unit pixel is about 4.8 × 5.5 μm. Since the size of the pattern portion 36a on the pixel on which only one of the red filter 33a, the blue filter 33b and the yellow filter 33c is formed is about 4.2 × 4.9 μm,
The size of the pattern portion 36b on the pixel on which the green filter is formed is set to about 4.1 × 4.8 μm.

In the case of a CCD type solid-state image pickup device having 380,000 pixels using a 1/6 inch optical system, the size of a unit pixel is about 3.20 × 3.75 μm, and a red filter is used. 33a, blue filter 33b or yellow filter 3
Pattern portion 36a on a pixel on which only any one of 3c is formed
Is about 2.80 × 3.35 μm, so the size of the pattern portion 36b on the pixel on which the green filter is formed is about 2.70 × 3.25 μm.

Next, as shown in FIG.
5 is developed, but the pattern portions 36a and 36 of the mask 36 are developed.
Since b has different sizes d ₁ and d ₆ ,
The pattern portion 35a on the pixel in which only the red filter 33a, the blue filter 33b, or the yellow filter 33c is formed, the halation effect or the like in the photoresist 35 is corrected, and the yellow filter 3b is formed on the blue filter 33b.
3c is a stacked pattern portion 35b on the pixel forming a green filter also has the same size d _2. 1

Next, as shown in FIG.
5 of the pattern portion 35a, 35b and is reflowed on-chip lens 37a, forms a 37b, the pattern portion 35a on one pixel, because 35b and have the same size d _2, on any pixel of On-chip lens 37a, 3
7b also have the same size d _4.

In the above embodiment, the positive photoresist 35 is used as the material layer of the on-chip lens, but a negative photoresist can be used. Also, the material of the on-chip color filter 33 can be freely selected.

In the above embodiment, the pattern portions 35a and 35b of the photoresist 35 are reflowed to form the on-chip lenses 37a and 37b. However, the entire surface is etched back after the photoresist is reflowed. The on-chip lens may be formed by transferring the shape of the resist to a material layer of the on-chip lens.

In the above-described embodiment, the on-chip color filter 33 is of a complementary color type. However, even an on-chip color filter of a primary color type having a single-layer structure generally has a different thickness for each color. The invention of the present application can be applied to the manufacture of a solid-state imaging device having a chip color filter.

In the above embodiment, the invention of the present application is applied to the manufacture of a CCD type solid-state imaging device.
The invention of the present application can be applied to the manufacture of a solid-state imaging device other than the D-type.

[0028]

According to the method of manufacturing a solid-state imaging device according to the present invention, the halation effect in the material layer of the on-chip lens can be obtained even if the underlayer of the material layer is not flat because the thickness of the on-chip color filter is not uniform. Can be corrected, and the shape of the on-chip lens of each pixel can be made uniform, so that a solid-state imaging device having excellent imaging characteristics such as a color sensitivity ratio and a color tone can be manufactured.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing an initial step of an embodiment of the present invention.

FIG. 2 is a side sectional view showing a middle stage process of the embodiment.

FIG. 3 is a side sectional view showing a final step of the embodiment.

FIG. 4 shows on-chip color filters according to an embodiment of the present invention and a conventional example, and FIGS.
(C) is a plan view sequentially showing a manufacturing process, and (d) is a plan view of a completed state.

FIG. 5 is a side sectional view showing an initial step of a conventional example of the present invention.

FIG. 6 is a side sectional view showing a middle stage process of a conventional example.

FIG. 7 is a side sectional view showing a final step of a conventional example.

[Explanation of symbols]

33a Red filter (on-chip color filter) 33b Blue filter (on-chip color filter) 33c Yellow filter (on-chip color filter) 35 Photoresist (material layer) 36 Mask 36a, 36b Pattern portion 37a, 37b
On-chip lens

Claims (4)

[Claims] 1. A method for manufacturing a solid-state imaging device having an on-chip color filter and an on-chip lens on an upper layer thereof in each pixel, wherein the size differs according to the thickness of the on-chip color filter for each pixel. Lithography is performed on the material layer of the on-chip lens using a mask having a patterned portion. 2. The method according to claim 2, wherein a positive photoresist is used as the material layer, and the pattern portion having a relatively small size corresponds to the on-chip color filter having a relatively large thickness. A method for manufacturing the solid-state imaging device according to claim 1. 3. The method according to claim 1, wherein the on-chip color filter having a laminated structure is formed. 4. The method according to claim 1, wherein the on-chip color filter having a single-layer structure is formed.