JPH10341012A - Manufacture of solid-state image-pickup element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drastically improve the characteristic of a color solid-state image- pickup element with the color filters of on-chip structures which are formed thereon using pigment resists. SOLUTION: For example, a pigment resist 22 with a red pigment previously distributed therein is applied on a silicon substrate 11 with a solid pickup element formed thereon. After applying a water-soluble resist 31 to the pigment resist 22, a resist 32 with a dry-etching resistance is further applied thereto. Then, a mask pattern 32a is formed by patterning the resist 32, the dry etching processings of the resists 31, 22 are performed to form a red filter layer 22'. Similarly, repeating the foregoing processes, pigment resists 23, 24 with respective green and blue pigments previously distributed therein are used to form green and blue filter layers 23', 24'.

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 sensor, and more particularly to a method for forming a filter used in a color solid-state image sensor.

[0002]

2. Description of the Related Art Hitherto, a filter using a pigment resist for a filter layer has been developed as a filter of a color solid-state imaging device. FIG. 3 schematically shows a method of forming a filter layer using a pigment resist, taking a color solid-state imaging device as an example. Here, the internal structure of the solid-state imaging device will be omitted and described.

First, a substrate 10 on which a solid-state image sensor is formed is provided.
1 is, for example, EEP which is an acrylic resin
A pigment resist 201 in which a red (R) pigment is dispersed in advance is applied to (ethoxy, propion, ethyl acid) so that the surface thereof is flat (see FIG. 3A).

The pigment resist 201 is exposed using a mask 301, and only the pigment resist 201a corresponding to the position where the R filter layer is formed is cured (see FIG. 1B).

Thereafter, the pigment resist 201 is developed to leave only the cured pigment resist 201a, thereby forming an R filter layer 201 'on the surface of the substrate 101 (see FIG. 1C).

Similarly, the above-described process is repeated to form the G and B filter layers 202 'and 203', respectively, thereby forming a solid-state imaging device having R, G and B color filters.

That is, for example, a pigment resist 202 in which a green (G) pigment is dispersed in EEP is applied to the surface of the substrate 101 on which the R filter layer 201 ′ is formed. Expose. Then, the pigment resist 202 is developed to leave only the portion of the pigment resist 202a corresponding to the position where the G filter layer is formed, thereby forming a G filter layer 202 ′ on the surface of the substrate 101 (FIG. d) to (f)).

Further, the R filter layer 201 'and the G
Is applied to the surface of the substrate 101 on which the filter layer 202 ′ is formed, for example, by applying a pigment resist 203 in which a blue (B) pigment is dispersed in EEP, and then exposing it using a mask 303. Then, the pigment resist 203 is developed to leave only the portion of the pigment resist 203a corresponding to the formation position of the B filter layer, thereby forming the B filter layer 203 'on the surface of the substrate 101 (FIG. g) to (i)).

As described above, in the above-described conventional color solid-state imaging device, the pigment resists 201, 202, and 203 are
By patterning by the so-called PEP (Photo Engraving Process), the filter layers 201 ', 202
', 203' respectively.

However, the filter layers 201 ', 2
Pigment resist 20 used for forming 02 ', 203'
1, 202, and 203 have poor resolution in patterning by PEP due to their characteristics, making it difficult to perform fine processing, and also have poor pattern shapes (profiles) of the filter layers 201 ', 202', and 203 '. There was a problem.

In patterning by PEP, unexposed portions (pigment resists 201a, 202) are developed.
a, 203a) pigment resists 201, 202, 2
03 is difficult to completely remove. For this reason, as shown in FIG. 4, for example, when a large part of the pigment resist that cannot be removed is present as a residue 401, the residue becomes dust, which has the disadvantage of deteriorating the characteristics of the solid-state imaging device. .

In particular, in the case of a color solid-state imaging device, the residue 40 on another pixel (where another filter layer is formed).
The presence of 1 has a great adverse effect on other pixels, such as causing color mixing.

In order to solve such a problem, at present, the residue 401 is removed by a physical cleaning process (so-called brushing) using a brush.

[0014]

As described above, in the prior art, it is difficult to finely process a pigment resist having a low resolution, not only the pattern profile of the filter is not excellent but also the generation of residues. There have been problems such as deterioration of the characteristics of the solid-state imaging device.

Accordingly, the present invention provides a solid-state image pickup device capable of finely processing a pigment resist, forming a filter layer having an excellent pattern profile without generating a residue, and improving the characteristics of the device. The purpose of the present invention is to provide a manufacturing method.

[0016]

In order to achieve the above object, a method for manufacturing a solid-state imaging device according to the present invention comprises the steps of:
A first step of forming a solid-state imaging device on a semiconductor substrate,
A second step of applying a pigment resist for forming a filter layer on the surface of the substrate on which the solid-state imaging device is formed; a third step of applying a water-soluble resist on the pigment resist; and A fourth step of forming a resist pattern having dry-etching resistance on the hydrophilic resist, and selectively etching the water-soluble resist and the pigment resist according to the resist pattern, thereby forming a filter layer made of the pigment resist. And a fifth step of forming

According to the method of manufacturing a solid-state imaging device of the present invention, a pigment resist having poor resolution is patterned by using a resist pattern having good resolution and dry etching resistance. As a result, the resolution of the pigment resist can be improved, and unnecessary pigment resist can be reliably removed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a solid-state imaging device having a color filter according to an embodiment of the present invention.

That is, this color solid-state image pickup device has, for example, a concave portion 12 on a silicon substrate (semiconductor substrate) 11.
Pixel portion 1 provided with a light receiving layer 13 for photoelectrically converting light incident on the pixel and generating electric charges corresponding to the intensity of the light.
4 are selectively provided.

A charge transfer section 15 for transferring charges generated in the light receiving layer 13 is provided between the pixel sections 14. This transfer unit 15
It comprises a transfer gate region 16 connected to the light receiving layer 13, a charge transfer region 17 connected to the transfer gate region 16, and a transfer gate electrode 18 for controlling these.

The charge transfer region 17 of the charge transfer portion 15 and the light receiving layer 13 of the pixel portion 14 adjacent to the charge transfer region 17 are formed.
A channel stop region 19 for separating them from each other is provided.

A light-shielding layer 20 for blocking light incident on portions other than the pixel portion 14 is provided in a portion corresponding to the transfer gate electrode 18 except for the recess 12. The light shielding layer 20 and the transfer gate electrode 18
A transparent insulating film 21 is formed around the light-receiving layer 13 and on the light-receiving layer 13.

Further, the concave portions 12 are provided with R, G, B filter layers 22 ', 23', 24 'made of a pigment resist for each pixel portion 14, thereby forming a color filter. .

The upper and lower surfaces of the filter layers 22 ', 23' and 24 'are arranged so that the surface of the element becomes flat.
It is covered with a transparent protective film 25. The color filter in the color solid-state imaging device having such a configuration is formed as follows.

FIG. 2 shows an outline of a method for forming a filter layer using a pigment resist, taking the color solid-state imaging device having the above-described configuration as an example. Here, the internal structure of the solid-state imaging device will be described with illustration omitted.

First, for example, EEP (ethoxy-propion-ethyl acid), which is an acrylic resin, is preliminarily placed on the silicon substrate 11 on which the solid-state imaging device is formed, so that the concave portion 12 on the surface is completely filled. A pigment resist 22 in which a red (R) pigment is dispersed is applied (see FIG. 3A).

Next, on the upper surface of the pigment resist 22,
A water-soluble resist (for example, a water-soluble acrylic resin obtained by adding pure water to isopropyl alcohol) 31 is applied (see FIG. 2B).

In this case, the water-soluble resist 31 functions as a buffer layer for preventing the surface of the pigment resist 22 from being damaged at the time of dry etching and removal of the mask pattern described later. , G, B filter layers 22 ', 23', 24
The pigment resist 22 (the filter layer 22 ') is formed thick enough so that the surface of the pigment resist 22 (the filter layer 22') is not damaged even by a slight over-etching in each dry etching process for forming the '.

Next, a resist (for example, a phenol-based resin mainly composed of EEP) 32 having dry etching resistance is applied to the upper surface of the water-soluble resist 31 (see FIG. 3C).

Next, the resist 32 having dry etching resistance is patterned to form a mask pattern (resist pattern) 32a for forming the R filter layer 22 '(see FIG. 4D).

Next, dry etching is performed in accordance with the mask pattern 32a to remove portions of the water-soluble resist 31 and the pigment resist 22 which are unnecessary for the formation of the R filter layer 22 'together with the mask pattern 32a. Then, an R filter layer 22 'is formed on the surface of the substrate 11 (see FIG. 3E).

At this time, as the etching process, R
The etching at the position where the filter layer 22 ′ is formed is controlled to be the end point in the water-soluble resist 31.
As a result, the R filter layer 22 'is formed on the surface without being damaged by etching.

Moreover, since the resist 32 having dry etching resistance is excellent in resolution, the pigment resist 22 can be finely processed and a filter layer 22 'having an excellent pattern profile can be formed.

Further, since the pigment resist 22 unnecessary for forming the R filter layer 22 'can be completely removed by the etching, the problem that a residue is generated can be solved.

As described above, the R filter layer 22
After the formation of the G and B filter layers 23 'and 24 by the pigment resists 23 and 24 in which the G and B pigments are dispersed, the formation of the G and B pigments is repeated.
Is formed, an on-chip color filter composed of R, G, and B filter layers 22 ', 23', and 24 'is formed.

That is, after the R filter layer 22 'is formed by partially leaving the pigment resist 22 on the surface of the substrate 11, the water-soluble resist 31
Is left as it is, for example, a pigment resist 23 in which a green (G) pigment is dispersed in EEP is further applied (see FIG. 7F).

Next, on the upper surface of the pigment resist 23,
For example, a water-soluble resist 33 composed of the same components as the water-soluble resist 31 is applied (see FIG. 3G). Also in this case, the water-soluble resist 3 functioning as a buffer layer is used.
3 is, for example, each of the G and B filter layers 23 ', 24
The pigment resists 22, 23 (filter layers 22 ', 23') can be formed by a slight over-etching in each dry etching process for forming the
Is formed thick enough not to damage the surface.

Next, for example, a resist 34 having the same composition as the resist 32 and having dry etching resistance is applied to the upper surface of the water-soluble resist 33 (see FIG. 3H).

Next, the resist 34 having dry etching resistance is patterned to form a mask pattern (resist pattern) 34a for forming the G filter layer 23 '(see FIG. 1I).

Next, a dry etching process is performed according to the mask pattern 34a to remove portions of the water-soluble resist 33 and the pigment resist 23 which are unnecessary for the formation of the G filter layer 23 'together with the mask pattern 34a. Then, a G filter layer 23 'is formed on the surface of the substrate 11 (see FIG. 3 (j)).

When the formation of the G filter layer 23 'is completed by partially leaving the pigment resist 23 on the surface of the substrate 11, the water-soluble resist 33 is then left on the G filter layer 23'. For example, EE
A pigment resist 24 in which a green (B) pigment is dispersed is further applied to P (see FIG. 9 (k)).

Next, on the upper surface of the pigment resist 24,
For example, a water-soluble resist 35 composed of the same components as those of the water-soluble resists 31 and 33 is applied (see FIG. 1 (l)). In this case as well, the water-soluble resist 35 functioning as a buffer layer can be formed on the pigment resist 22 by a slight over-etching process in the dry etching process for forming the B filter layer 24 '.
The surface of each of the filter layers 23 and 24 (the filter layers 22 ', 23' and 24 ') is formed thick enough so as not to be damaged.

Next, on the upper surface of the water-soluble resist 35, for example, a resist 36 having the same components as the resists 32 and 34 and having dry etching resistance is applied (see FIG. 3 (m)).

Next, the resist 36 having dry etching resistance is patterned to form a mask pattern (resist pattern) 36a for forming the B filter layer 24 '(see FIG. 3 (n)).

Next, a dry etching process is performed according to the mask pattern 36a to remove portions of the water-soluble resist 35 and the pigment resist 24 which are unnecessary for the formation of the B filter layer 24 'together with the mask pattern 36a. Then, a B filter layer 24 'is formed on the surface of the substrate 11 (see FIG. 2 (o)).

Thus, each of the R, G, B filter layers 2
After sequentially forming 2 ', 23', and 24 ', the water-soluble resists 31, 33, and 35 are washed away to remove the water-soluble resists 31, 33, and 35, and mask patterns 32a, 34a, and 36a on the surface thereof. If remains, remove it as well.

Also in this case, the surface of each of the R, G, and B filter layers 22 ', 23', and 24 '
No damage is caused by the removal of 2a, 34a, 36a.

The R, G, B filter layers 22
By forming the transparent protective film 25 so as to cover ′, 23 ′, and 24 ′, the color solid-state imaging device having the structure shown in FIG. 1 is configured.

The color filter having an on-chip structure formed by such a process can not only be fine and have an excellent pattern profile, but also can be formed without generating a residue. This makes it possible to improve the characteristics of the solid-state imaging device.

As described above, a pigment resist having poor resolution is patterned by using a resist pattern having good resolution and dry etching resistance. That is, when a color filter having an on-chip structure is formed using a pigment resist, patterning is performed using an anti-dry etching resist. As a result, the resolution of the pigment resist can be improved, so that a fine filter layer having an excellent pattern profile can be formed.

Further, since the pigment resist unnecessary for forming the filter layer can be surely removed by etching, no residue is generated. Therefore, the characteristics as a color solid-state imaging device can be significantly improved.

In the above-described embodiment of the present invention, the case where the present invention is applied to a color solid-state imaging device has been described as an example. However, the present invention is not limited to this, and can be similarly applied to, for example, a monochrome solid-state imaging device.

Although each filter layer as a color filter is formed in the order of R, G, and B, the order and arrangement of the formation are not limited at all.
Of course, various modifications can be made without departing from the scope of the present invention.

[0054]

As described in detail above, according to the present invention, a pigment resist can be finely processed and a filter layer having an excellent pattern profile can be formed without generating a residue. It is possible to provide a method for manufacturing a solid-state imaging device that can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a main part of a configuration of a solid-state imaging device including a color filter according to an embodiment of the present invention.

FIG. 2 is also a schematic cross-sectional view for explaining a method of manufacturing such a color filter.

FIG. 3 is a schematic cross-sectional view showing a method of manufacturing a color filter using a pigment resist for explaining a conventional technique and its problems.

FIG. 4 is a schematic sectional view showing a main part of a conventional color solid-state imaging device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Silicon substrate 12 ... Concave part 13 ... Light receiving layer 14 ... Photosensitive pixel part 15 ... Charge transfer part 16 ... Transfer gate area 17 ... Charge transfer area 18 ... Transfer gate electrode 19 ... Channel stop area 20 ... Light shielding layer 21 ... Insulating film 22, 23, 24 ... Pigment resist 22 ', 23', 24 '... Filter layer 25 ... Protective film 31, 33, 35 ... Water-soluble resist 32, 34, 36 ... Resist 32a, 34a, 36a having dry etching resistance … Mask pattern

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 9/07

Claims (4)

[Claims] 1. A first step of forming a solid-state image sensor on a semiconductor substrate, and a second step of applying a pigment resist for forming a filter layer on a surface of the substrate on which the solid-state image sensor is formed. A third step of applying a water-soluble resist on the pigment resist; a fourth step of forming a resist pattern having dry etching resistance on the water-soluble resist; and A fifth step of selectively etching the water-soluble resist and the pigment resist to form a filter layer made of the pigment resist. 2. The method according to claim 1, wherein in the fifth step, when the water-soluble resist and the pigment resist unnecessary for forming the filter layer are etched, the resist pattern is simultaneously etched. 3. The method for manufacturing a solid-state imaging device according to item 1. 3. The method according to claim 1, further comprising removing the water-soluble resist remaining on the filter layer after the fifth step. 4. The method according to claim 1, wherein a color filter layer is formed by repeating the second to fifth steps.