JPH01276666A - Solid state image pickup device - Google Patents

Abstract

PURPOSE:To obtain a solid state image pickup device employing a bottom type photoelectric transducer having an on-chip filter with excellent characteristics by providing a color separation filter made of polyimide as base material between an insulating transparent substrate and the photoelectric transducer. CONSTITUTION:A dyed polyimide layer 121 is formed on an insulating transparent substrate 111. Further, dyed polyimide layers 122 and 123 with different colors are formed to provide a three-color dyed polyimide filter. With this constitution, an on-chip filter having excellent characteristics and heat-resistant properties sufficient to form a photoelectric converting element 101 can be produced and an on-chip filter type solid state image pickup device employing the photoelectric converting element which has excellent color separation characteristics and to which a light is applied from the substrate side can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to filters and other structures of solid-state imaging devices.

[Prior art] There are two types of photoelectric conversion elements used in solid-state imaging devices: one type in which light enters from the side opposite to the substrate, and the other type in which light enters from the substrate side (hereinafter this type is referred to as the bottom type).
There is.

Since a non-transparent substrate such as a semiconductor substrate can be used for the former, this type of photoelectric conversion element is often used in the -film. In this type, the surface on which light enters and the element surface are on the same side, so if there is dirt on the entrance surface that affects the read image, it is very difficult to remove it without affecting each element. It's difficult. For this reason, it is usually sealed in a container made of a transparent material such as glass and has a window. Since the solid-state imaging device used in the same-magnification imaging system is large, it is difficult to enclose it in a container like this, resulting in high cost.

Therefore, the latter type of charging conversion element is often used in solid-state imaging devices for such uses.

In this case, it is necessary to use a transparent substrate such as glass or quartz, but the above-mentioned problem does not occur. In other words, the incident surface side is simply the surface of an insulator such as glass, and cleaning this portion is relatively easy. Further, even if dirt or the like adheres to the element surface side, there is almost no effect on the reading of the solid-state imaging device, and the device can be used in a simple mounting form.

Incidentally, a so-called filter-on-chip solid-state imaging device in which a color separation filter is formed directly on a charging conversion element is very useful for reading color images. For this reason, even when using a 1-magnification telephoto imaging system, it is possible to use a solid state camera using a bottom-type photoelectric conversion element as described above.
There is a demand for a filter-on-chip type of S-image device.

Currently, the methods for forming this on-chip filter are: (A) providing a dyeable polymer film such as gelatin or polyvinyl alcohol and dyeing it; (B) forming a pattern using a transparent conductive layer; A method is known in which a polymer in which a pigment is dispersed is electrodeposited.

However, the filter made by method (A) has very low heat resistance and cannot withstand the processing temperature required to form a photoelectric conversion element, and the filter made by method (B) has very low heat resistance. Although the heat resistance is higher than that obtained by this method, sufficient filter properties cannot be obtained because a pigment is used as a coloring agent.

Therefore, the present invention is intended to solve such problems.
The objective is to realize a solid-state imaging device using a bottom-type charging conversion element with an on-chip filter with good characteristics.

[Means for Solving the Problems] In order to solve the above problems, the solid-state imaging device of the present invention includes a color separation filter made of polyimide as a base material, which is provided between the insulating transparent substrate and the photoelectric conversion element. It is characterized by:

Furthermore, in order to reduce the number of man-hours, the present invention is characterized in that the filter layer made of the above-mentioned polyimide is used as an interlayer insulating film.

[Example ] The present invention will be explained below with reference to Examples.

FIG. 1 is a cross-sectional view showing a method for forming a solid-state imaging device according to an embodiment of the present invention in order of steps.

FIG. 1(a) shows a state in which a dyed polyimide layer 121 is formed on an insulating transparent substrate 111.

Normally, a polyimide layer is formed by dissolving polyamic acid in a solvent such as N-methylpyrrolidone (NMP), 2-methoxyl, or cyclohexanone, and applying it using a spin cord.
This can be done by curing at high temperature and imidizing. The dyed polyimide layer is formed by the process described above by adding a dye soluble in the solvent when polyamic acid is dissolved in the solvent. The polyimide used as the base material is preferably transparent, but it can be used as long as the light absorption range of the polyimide is within or near the light absorption range of the dye used. It is also possible to form a colored polyimide layer using a similar method using a pigment instead of a dye as a coloring agent, but this is only possible if high-temperature heat treatment is required in the post-process because the properties of the resulting filter are limited. used.

The curing temperature during formation of the dyed polyimide layer shown in FIG. 1(a) is set at 120 to 160° C., so that it is not completely imidized. Next, this dyed polyimide layer is patterned to obtain a mosaic or striped multicolor filter.

Patterning can be performed by a normal photolithography process using a positive resist, as shown in Figure 1(b).
The state shown in is reached. Since the polyimide layer with a low imidization rate is soluble in a positive resist developer, the polyimide layer can be etched at the same time as the positive resist is developed.

The patterning process of the dyed polyimide layer of the first color is completed by peeling off the positive resist layer 131 with a stripping solution using ethyl acetate, butyl acetate, or the like.

When polyimide is cured at a temperature of 180 to 200°C or higher, imidization progresses and it becomes insoluble in most solvents including NMP and the like. Therefore, if the dyed polyimide layer of each color is buttered and then cured at 180 to 200℃ or higher, even if the same process is repeated to form a dyed polyimide layer of a different color, the previously formed dyed polyimide layer will be reused. It is not dyed or etched.

However, in this case, the curing temperature was set at 200 to 250°C, since treatment at a very high temperature was not possible due to the heat resistance of the dye.

Thereafter, similar steps are repeated to form dyed polyimide layers 122 and 123 of different colors, thereby making it possible to form a filter made of dyed polyimide in three colors as shown in FIG. 1(C).

In this example, a case has been described in which filters of three colors are formed, but it is possible to form filters of any number of colors by repeating the same steps.

Before forming the photoelectric conversion element, a buffer layer 113 made of an inorganic material such as S, 02, S, or Nx is formed on the filter. This is to improve the adhesion between the filter and the transparent conductive layer 114 of the lower electrode of the photoelectric conversion element, and the subsequent steps can be performed without providing it.
The buffer layer has a suitable thickness of about 1,000 to 6,000 layers, and is formed by a sputtering method or a plasma CVD method that can be formed at a temperature below the curing temperature of polyimide.

This is not only due to the heat resistance of the dye, but also because the imidization of the dyed polyimide layer is not complete at a processing temperature of around 250°C, and as the processing temperature increases, imidization progresses, causing the film to shrink, become wavy, and peel off. It's for a reason.

a lower electrode formed of a transparent conductive layer 114 on the buffer layer;
A photoelectric conversion element 101 including an upper electrode formed of a photoconductive layer 115 and a conductive layer 116 is formed.

The transparent conductive layer was formed by a sputtering method using ITO as an element material, the photoconductive layer was formed by a plasma CVD method using a-9: as an element material, and the conductive layer was formed by a sputtering method using Al-81-Cu as an element material, and then processed. The temperature is made not to exceed the curing temperature of the dyed polyimide layer, 200 to 250°C.

After this, three passivation layers 117.118.11
9 is formed to complete the manufacturing process of this solid-state imaging device, and the image shown in FIG. 1 (y-axis) is obtained.

FIGS. 2(a) and 2(b) are cross-sectional views showing another embodiment of the solid-state imaging device according to the present invention, in which a scanning circuit using thin film transistors 202 is integrated on the same substrate. The example shown in FIG. 2(a) is manufactured by performing the above-mentioned steps after forming the interlayer insulating film 212 during the thin film transistor manufacturing process. Conductive 1' which forms the upper electrode of the photoelectric conversion element! ! Reference numeral 216 is commonly used as wiring for the scanning circuit.

In FIG. 2(b), a dyed polyimide layer is formed immediately after the manufacturing process of the thin film transistor is completed, so that the dyed polyimide layer plays the role of the interlayer insulating film, thereby reducing the number of steps. Polyimide has high insulation properties, heat resistance, and good step coverage, so it can be widely used for insulation between the eyebrows of semiconductor devices.

[Effects of the Invention 1] As described above, the present invention makes it possible to produce an on-chip filter that has heat resistance and good properties that can be used to make photoelectric conversion elements, and also allows the production of on-chip filters that have good color separation properties from the substrate side. It has become possible to realize an on-chip filter solid-state 111 device using a photoelectric conversion element that allows light to enter.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(e) are cross-sectional views showing a method for forming a solid-state imaging device according to an embodiment of the present invention in the order of steps. FIGS. 2(a) and 2(b) are cross-sectional views showing another embodiment of the solid-state imaging device of the present invention, in which a scanning circuit using thin film transistors is integrated on the same substrate. Figure 2(b)
This is an example in which a dyed polyimide layer is further used as an insulating film between the eyebrows of a thin film transistor. 101 ...... Photoelectric conversion element 111.2
11 ...... Insulating transparent substrate 113.2
13...Buffer layer 114.21
4 ...... Transparent conductive layer (lower electrode) 115.215 ...... Photoconductive layer 116
...... Conductive layer (upper electrode) 117.217 ...... Passivation layer first layer 118
．． 218 ...... Passivation layer second layer 119
．． 219 ・・・・・・Pudgebage Yon layer 3rd layer 12
1.122.123.221 ...... Dyed polyimide layer 202
...... Thin film transistor 212
...... Interlayer insulating film 216
...... Conductive layer (upper electrode and inter-element wiring 222) Dyed polyimide layer (filter and interlayer insulating film) Applicant: Seiko Epson Co., Ltd. Attorney Masayoshi Kamiyanagi (and 1 other person) (a) (b) Figure 1 (d) Figure 1

Claims (2)

[Claims] (1) In a solid-state imaging device in which photoelectric conversion elements are formed on an insulating transparent substrate in a format in which light enters from a plurality of substrate sides, a polyimide-based material is used between the insulating transparent substrate and the photoelectric conversion elements. A solid-state imaging device characterized by being provided with a color separation filter as a material. (2) The solid-state imaging device according to item 1, wherein the filter layer made of polyimide as a base material is used as an interlayer insulating film.