JPS61120586A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To prevent deterioration of a laminated photoconductive film by forming an insulation layer smoothing a rugged plane of a semiconductor substrate with an organic insulation layer and an inorganic insulation layer and to attain ease of taper etching of a contact hole through the structure of the inorganic insulation layer. CONSTITUTION:A scanning part and the 1st electrode 8 are formed on a semiconductor substrate 1 and its surface is made coarse. Then a heat-resistant organic insulation layer 14 is coated on the coarse face and laminated to a height higher than the top of the electrode 8 by nearly 1,000Angstrom . Then the organic insulation layer 14 is formed on the recess of the substrate 1 to form the inorganic insulation layer 15 on the elec trode 8 and the organic insulation layer 14. Then a contact hole 10 is provided to the insulation layer 15, and after an Al-Si is vapor-deposited on the entire face on the insulation layer 15, the 2nd electrode 11 is formed. Then a photoconductive film 12 is laminated on the electrode 11. Since the insulation layer 15 is formed while smoothing the rugged plane of the substrate 1 by the insulation layer 14, it is not required to polish the insulation layer 15. The photoconductive film 12 is not contami nated by the insulation layer 14 by the intervention of the insulation layer 15. Since the contact hole 10 is formed in contact with the insulation layer 15 only, taper etching is attained easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a solid-state imaging device in which photoconductive films are laminated.

[Technical background of the invention]

In recent years, solid-state imaging devices have been developed in which a photoconductive film is provided on a semiconductor substrate on which a scanning section and the like are formed, and signal charges generated in the photoconductive film are read out by the scanning section.

FIG. 3 is a diagram showing an example of this type of solid-state imaging device,
The P semiconductor substrate (1) contains C consisting of n+ type impurities.
An OD channel (2) and a charge storage section (3) are provided adjacent to each other, and this integrated structure is separated from each other (partially) by a stopper region (4) C of the P+ board.

A gate electrode (6) is formed on the semiconductor substrate (1) excluding the charge storage portion (3) via a gate insulating film (5), further covering the gate electrode (6) and covering the charge storage portion ( 3) An insulating film is formed so that a part of it is exposed.

Further, on the charge storage section (3) and the insulating film (7), first electrodes (8) are formed for each pixel (partially separated).

In this way, the surface of the semiconductor substrate (1) has an uneven surface, but in order to smooth this uneven surface, StO, Si, etc.
An insulating layer (9) made of an inorganic insulating material such as N4 or a heat-resistant polyimide-based organic insulating material is formed. A contact hole 4 is provided in a part of the insulating layer (9), and the first electrode (8) is electrically connected through this contact hole. 9) A second electrode (Ll) is formed on the insulating layer (9) and the second electrode 5; Condylar formation.

In this solid-state imaging device, when a photoconductive film 1 is irradiated with a predetermined voltage applied to the eighth electrode (L: 1),
Signal charges photoelectrically converted are generated in the photoconductive film @, and these signal charges are transferred to the first electrode (8) and the second electrode (11).
The charge storage section (3) C is accumulated through J.

The accumulated signal charges are then read out from the COD channel (2)C by applying heavy pressure to the first gate electrode (6) after an arbitrary accumulation time.

[Problems with background technology]

The above-mentioned solid-state imaging device has the advantage that cracks do not occur inside the formed photoconductive film C1aC because the unevenness of the underlying surface when forming the photoconductive film C1a is reduced by the insulating layer (9). On the other hand, it is clear that there are the following problems.

That is, for example, when the insulating layer (9) is made of an inorganic insulating material,
The insulating layer (9) is deposited by sputtering or electron beam evaporation, but even if the film thickness is 10 μm, it is affected by the unevenness of the underlying semiconductor substrate (1) and does not become flat.

Therefore, polishing is performed to smooth the gate electrode (6), but it is difficult to obtain precision during polishing, and in some cases, the gate electrode (6)
There is also a risk of damaging the scanning unit.

On the other hand, when the insulating layer (9) is made of a heat-resistant organic insulating material, the insulating layer (9) can be deposited by a solution film forming method, and if the viscosity is appropriately adjusted, it can be spin-coated with a spinner and smoothed. It's easy to do.

However, the photoconductive film resistance is easily affected by the underlying material, and when an organic insulating material is exposed between the second electrode beams that separate the pixels, it is less likely to be formed than when it is an inorganic insulating material. The photoconductive film 0 has weak adhesion, and its dark specific resistance is one to two orders of magnitude smaller. This means that leakage between the second electrodes αυ is likely to occur, resulting in deterioration of resolution and images. In addition, trace amounts of contaminants such as residual solvents and gas components contained in the organic insulating material seep out from the photoconductive film (I3+2), causing the photoconductive
It may also deteriorate the characteristics of the product and shorten its lifespan.

[Purpose of the invention]

The present invention has been made to solve these conventional drawbacks, and it is possible to prevent the deterioration of the characteristics of the photoconductive film and to improve the electrical connection between the 14th pole and the 2':/1 pole. The purpose of the present invention is to provide a solid-state imaging device that can perform two functions.

[Summary of the invention]

That is, the present invention provides a semiconductor substrate having an uneven surface (concave and convex) with poles formed on the scanning section and the first and second parts, a heat-resistant organic insulating layer formed in the concave portions of the uneven surface, and an inorganic insulating node formed on the 1st electrode and the M organic insulating layer, and a second electrode electrically connected to the first electrode via a contact hole provided in a part of the inorganic insulating layer; This is a solid-state imaging device characterized by comprising a photoconductive film laminated on the second electrode side and a translucent eighth electrode formed on the photoconductive film.

[Embodiments of the invention]

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, and the same parts as in FIG. 8 are given the same reference numerals. This example is the first
As shown in the figure, a P-type semiconductor substrate (1) has a COD channel (2) made of all impurities and a charge storage part (3).
) are provided adjacent to each other, and this integrated structure is separated from each other by a distance C from the P-type stopper region (4) c. And the semiconductor substrate (1) excluding the charge storage part (3)
A gate electrode (6) is formed on the top via a gate insulating film (5).
is formed, and a ≦2 insulating film (7) is formed so as to cover the C ngate electrode (6) and expose a part of the charge storage part (3). In addition, the charge storage part (3) and the insulating film (7)
), a first electrode (8) is formed separately for each pixel. In this way, the scanning portion and the first electrode (8) are formed on the semiconductor substrate (1), and the surface thereof becomes an uneven surface 62.

Then, a heat-resistant organic insulating layer a◆, for example, polyimide, is spin-coated on this uneven surface using a spinner to form a portion 1000λ higher than the top of the first electrode (8). Next, the entire surface of the organic insulating layer I is etched by a dry etching method while controlling the progress. Note that this etching is controlled by measuring changes in the light reflectance of the organic insulating layer I, and the top of the first electrode (8) is
Complete the process with a thickness of approximately i exposed. Next, the semiconductor substrate (1) is placed in a vacuum furnace at a temperature of about 400C for about 1
Baking is performed for a period of time to solidify and degas the organic insulating layer I. At this time, moisture, residual solvent, etc. are released from the organic insulating layer I as a gas, but it cannot be completely removed, and in the long term, the organic insulating layer I will seep out from the narrow surface (narrow surface) of the semiconductor substrate (1). Organic insulating layer (14) in the concave part of the uneven surface
is formed. Next 6: First electrode (8) and organic insulating layer I
On top, an inorganic insulating layer (LS, for example, another 11N4) is formed. This inorganic insulating layer US is heated at a pressure of 1.0 Torr and a temperature of 25
3iH4, Hl and NH8 under the conditions of 0C and power 4W
The three types of gases are decomposed by glow discharge and deposited to a thickness of about xoooi. Next, at a predetermined position of the inorganic insulating layer a$,
Contact hole α0 by chemical dry etching
will be established. Next, person 4-81 was inorganic insulated tfj (15
Upper entire surface C: After vapor deposition, the second electrode I is formed by etching into a predetermined shape. This second electrode αη is electrically connected to the first electrode (8) through a contact hole (1G) provided in a part of the inorganic insulating layer a.
The second electrode aυ side, that is, the inorganic insulating layer (15 and the second electrode μυ
An amorphous silicon film is laminated thereon as a photoconductive film (L).The pressure of this photoconductive film 0 is 2.0 Torr.

Under conditions of temperature 250C and power 8W, glow discharge decomposition of 8iH4 diluted with 10% Hl and up to ppm of BtHa is performed to a thickness of about 8μm;
The dark resistivity becomes about 10 to 10Ωα. Then, at the upper end of the photoconductive film α, ITO is formed as a transparent third electrode (13) by sputtering, and a desired solid-state imaging device is obtained.

In this example, the uneven surface of the semiconductor substrate (1) is covered with an organic insulating layer (
Since the inorganic insulating layer Qj is formed after being smoothed to a certain extent by step 9,), there is no need to polish the inorganic insulating layer (Is). Since the inorganic insulating layer (US) is sandwiched between the photoconductive film and the organic insulating layer (14), it is possible to prevent the photoconductive film from being contaminated by the organic insulating layer (14). C: Since the contact hole is formed in contact with the inorganic insulating layer by μm, it is easy to taper and control the size. Therefore, electrical defects between the first electrode (8) and the second electrode I are reduced.

[Other embodiments of the invention]

FIG. 2 shows another embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

This embodiment has almost the same structure as the embodiment shown in FIG. 1 except for the inorganic insulating layer, so the explanation will be limited to the inorganic insulating layer. In this embodiment, the inorganic insulating layer end consists of a plurality of layers, for example two layers,
These two layers have a thickness of approximately 10 mm in order from the side closest to the first electrode (8).
A first inorganic insulating layer (161) made of 00^ SiN, and a second inorganic insulating layer (ISt) made of 8+01 with a thickness of about 10001. And these two layers are @CC501
The etching rate for the dry etching when forming the contact hole (II) is the same as that of the first inorganic insulating layer (II).
161) is better! JI2 inorganic NA edge layer (larger than 16 mm).

This embodiment not only has the same effect as the embodiment shown in FIG. This prevents the electrode υ from being electrically shorted. On the other hand, in the case shown in FIG. 1, the inorganic insulating layer (to) is a single layer, so simple C: if it is formed thickly, the contact hole a1
This is inconvenient because the taper angle becomes steep. In addition, the inorganic insulating layer αe is a different type of layer (16
1), (16) are sea-based so that the C etching rate increases in order from the side closer to the first electrode (8), so taper etching with a gentle taper angle is possible, and ) and the second electrode α■.

Although not shown in the figure, the second electrode aυ and the second electrode aυ
On the inorganic insulating layer (1Ee) exposed from between, SiC having a thickness of, for example, xboii degrees may be formed as an electrode coating layer by a glow discharge decomposition method. Since no interfacial reaction occurs with the photoconductive film, the properties of the photoconductive film are further improved.

However, the thickness of the electrode coating layer is 20 mm so that the signal charge generated within the photoconductive film reaches the second electrode layer.
0 Å or less (preferably 2).

In the above-described embodiments, amorphous silicon was used as the photoconductive film; however, the present invention is not limited to this, and Sb, S,
8e-As-Te, Cd8e and CdZnT
It is clear that In8b, etc. can also be used.
Infrared photoelectric materials such as Pb8nTe and CdHgHe can also be used.

Further, although an interline transfer type COD is shown as an example of the scanning unit, the present invention is not limited to this, and a frame transfer type CCD, MO8 type CID, BBD, or a combination thereof may be used.

〔Effect of the invention〕

As explained above, in the solid-state imaging device of the present invention, since the insulating layer that smoothes the uneven surface of the semiconductor substrate is composed of an organic insulating layer and an inorganic insulating layer, deterioration of the laminated photoconductive film can be prevented. . Furthermore, by devising the structure of the inorganic insulating layer, a contact hole for electrically connecting the first electrode and the second electrode can be etched with a good taper.

[Brief explanation of drawings]

1 and 2 are diagrams showing an embodiment of the present invention, and FIG. 8 is a diagram showing an example of a conventional solid-state imaging device. (1)...Semiconductor substrate (Ll)...Second electrode Cl7J...Photoconductive film J...'! J18 magnetic pole (14)...Organic insulating layer 4, (Le...Inorganic insulating layer Agent Patent attorney Noriyuki Chika (and 1 other person) No.
1 Figure 2 Figure 3 Procedural amendment (voluntary) Showa 6 oji. , ＾ day

Claims (2)

[Claims] (1) A semiconductor substrate having an uneven surface on which a scanning portion and a first electrode are formed; a heat-resistant organic insulating layer formed in the recesses of the uneven surface; an inorganic insulating layer formed on an insulating layer; a second electrode electrically connected to the first electrode via a contact hole provided in a part of the inorganic insulating layer;
A solid-state imaging device comprising: a photoconductive film laminated on an electrode side; and a translucent third electrode formed on the photoconductive film. (2) The inorganic insulating layer is composed of a plurality of layers, and each layer is arranged so that the etching rate increases in order from the side closer to the first electrode. The solid-state imaging device described.