JPH02166769A - Laminated solid state image sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent a transparent electrode from being etched in case of etching an optically shielding layer and to optimally set the thickness of a film by forming the transparent electrode on the optically shielding layer to be patterned by etching. CONSTITUTION:An optically shielding layer 41 such as a thin Ti film is formed on the whole surface of a photoconductive film 30 by depositing, etc. The thickness of the optically shielding layer 41 is required for 1000Angstrom or more for sufficiently shielding a light. Then, a mask 43 is formed on the optically shielding layer 41 on an optical black region. Thereafter, the optically shielding layer 41 is selectively etched with acid etchant such as hydrochloric acid. In this case, since the photoconductive film 30 is not substantially etched, the photoconductive film 30 is not damaged in case of etching the optically shielding layer 41. Subsequently, an ITO electrode 42 is formed on the whole surface of a deposited layer, etc. Thus, change of spectral sensitivity due to variation in the thickness of the film at the time of etching of the optically shielding layer 41 of the ITO electrode 42 does not occur.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a solid-state imaging device in which a photoconductive film is laminated on a solid-state imaging device chip, and in particular aims to improve the optical black area. The present invention relates to a stacked solid-state imaging device and a manufacturing method thereof.

(Prior art) A solid-state imaging device with a two-story structure (stacked solid-state imaging device) in which a photoconductive film is laminated on a solid-state imaging probe chip is capable of widening the aperture area of the photosensitive section, so it is It has excellent features of high sensitivity and low smear.For this reason, this solid-state imaging device is seen as a promising camera for various surveillance televisions and high-definition televisions.Photoconductive film for stacked solid-state imaging devices At present, an amorphous material film is used.For example, 5e-As-Te
film, Zn5e-ZnCdTe film, a-81:H film (
hydrogenated amorphous silicon film), etc. Among these materials, especially due to their good properties, workability, and possibility of low-temperature formation,
The a-8t:H film is becoming the favorite.

By the way, in a solid-state imaging device, an optical black area of about several tens of pixel columns is formed on one side of the periphery of the image area. This optical black area is made up of pixels that are shielded from light, and is necessary to define the black level of the image signal, that is, the dark current. In other words, in a solid-state imaging device, even when no light is incident, electrical charges are thermally generated within the semiconductor that constitutes the solid-state imaging device, and this electrical charge is transferred to the signal charge storage section of each pixel along with the signal charges generated by the light. is accumulated in Therefore, in order to detect only the optical signal charge, it is necessary to provide a pixel shielded from light and extract the thermal signal charge component using this pixel.

In a stacked solid-state imaging device, a light shield layer made of Al, Ti, or the like is provided on a photoconductive film as an optical black region. FIG. 6 is a sectional view showing a schematic configuration of a conventional stacked solid-state imaging device. A pixel electrode 62 is formed on a semiconductor substrate 61 on which a signal charge storage section, readout section, transfer section, etc. are formed.
are formed into an array. A photoconductive film 63 made of amorphous silicon or the like is laminated on the pixel electrode 62.
Further, on the photoconductive film 63, ITO (Indluw+
A transparent electrode 64 made of tin oxide or the like is formed. The thickness of the transparent electrode 64 must be 300 to 500 times thinner to minimize reflection at the electrode 64. A light shield layer 65 made of a Ti thin film or the like is formed on the transparent electrode 64 to form an optical black region.

Here, when forming the optical shield layer 65, first the IT
A Ti thin film is deposited on the entire surface of the O electrode 64. After that, this Ti thin film is selectively etched using an etching solution,
Remove areas other than optical black areas. At this time, the optical shield layer 65 needs to have a thickness of 1000 Å or more in order to sufficiently shield light. When completely etching a Ti thin film with such a thickness, the ITO electrode 64
It is also slightly etched.

When the film thickness of the ITO7r5 electrode 64 changes, the ITO electrode 6
Since the spectral reflectance of light at 4 changes, the spectral sensitivity of the imaging device itself changes. Due to the change in spectral sensitivity due to the change in the film thickness of the ITO electrode 64, the spectral sensitivity of the solid-state imaging device deviates from the optimal spectral sensitivity adjusted by controlling the ITO film thickness, and also remains constant with good reproducibility. It becomes difficult to obtain a spectral sensitivity of

Note that in order to prevent changes in spectral sensitivity due to changes in the film thickness of the ITO electrode 64, it is necessary to
It is necessary that the thickness change of the TO electrode 64 be 10 Å or less. In order to reduce the thickness change of the ITO electrode 64 to 10 Å or less, the etching time of the light shield layer 65 is set to the etching time for the film thickness plus 50% of that time, and the film thickness of the light shield layer 65 is set to 100 Å or less. In this case, the etching ratio between the optical shield layer 65 and the ITO electrode 64 may be 50 or more. However, such ITOr1t
Light shield layer 65 with a large etching ratio with i64
Since there was no etching solution available, it was not possible to prevent changes in spectral sensitivity due to etching of the ITO m electrode 64.

(Problems to be Solved by the Invention) As described above, in conventional stacked solid-state imaging devices, the spectral sensitivity is There are problems in that the spectral sensitivity changes greatly, there is no reproducibility of the spectral sensitivity, and it is difficult to adjust the spectral sensitivity to the optimum value.

The present invention has been made in consideration of the above circumstances, and its purpose is to prevent changes in the thickness of the transparent electrode, to optimally set the thickness of the transparent electrode, and to improve spectral sensitivity with reproducibility. An object of the present invention is to provide a stacked solid-state imaging device that can be well adjusted to optimal sensitivity.

Another object of the present invention is to provide a method for manufacturing a stacked solid-state imaging device having the above characteristics.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to provide a light shield layer that is patterned by etching in order to prevent a transparent electrode from being etched during etching of the light shield layer. The purpose is to form a transparent electrode on top of the .

That is, the present invention provides a solid-state imaging probe chip in which a signal charge storage section and a signal charge readout section are formed on a semiconductor substrate, and a pixel electrode electrically connected to the signal charge storage section is formed on top of the signal charge storage section and signal charge readout section. , a stacked solid-state imaging device in which a photoconductive film as a photoelectric conversion section is stacked, and a transparent electrode and a light shield layer as an optical black region are formed thereon; The shield layer is a light shield layer.

The transparent electrodes are formed in this order.

The present invention also provides a method for manufacturing a stacked solid-state imaging device, in which a signal charge storage section and a signal charge readout section are formed on a semiconductor substrate, and a pixel electrode electrically connected to the signal charge storage section above the signal charge storage section. After laminating a photoconductive film as a photoelectric conversion section on the solid-state image sensor chip formed with
A conductive light shield layer is formed on the photoconductive film, and then the light shield layer is etched away except on the optical black area of the photoconductive film, and then a conductive light shield layer is formed on the photoconductive film and the light shield layer. This is a method for forming transparent electrodes.

(Function) According to the present invention, since the transparent electrode is located on the light shield layer, the transparent electrode is not etched when the light shield layer is etched to form an optical black region.

Therefore, the thickness of the transparent electrode is determined by the thickness at the time of formation. Therefore, the film thickness of the transparent electrode can be optimally set, and the spectral sensitivity can be adjusted to the optimal sensitivity with good reproducibility. Further, the base for etching the light shield layer is a photoconductive film, but since this photoconductive film is sufficiently thick, even if it is etched to some extent, it hardly causes any problem.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a sectional view showing a schematic structure of a stacked solid-state imaging device according to a first embodiment of the present invention.

In the figure, reference numeral 10 denotes a Si substrate, and on this substrate lo are formed chip elements 2o such as storage diodes, charge transfer sections, transfer gates, extraction electrodes, etc., which will be described later.
9 are arranged to form a plurality of solid-state image sensor chips. A photoconductive film 3o is laminated on these solid-state image sensor chips. The photoconductive film 30 is of the (a-81:H) system and has a three-layer structure of 31.32.33.

31 is i-type amorphous hydrogenated silicon carbide (a-9
IC: 1f(1)), thickness 200, 32 is i-type amorphous hydrogenated silicon (a-81:H(1)), thickness 3μ
m, 33 is p-type amorphous hydrogenated silicon carbide (
a-9IC: 11(p)) with a thickness of 200 people.

And photoelectric conversion is mainly a-8l:11(1) layer 3
It is done in 2.

Note that one pixel of the solid-state image sensor chip is configured as shown in FIG. That is, as shown in FIG.
0, an element isolation layer 21, an n+ type channel (vertical CC
After forming a D channel) 22 and an n++ type storage diode 23, transfer gates 24 and 25 are formed thereon.

Here, a part of the transfer gate 24 becomes a signal readout gate. Next, after forming a first insulating film 26 of 5 in 2 or the like, a contact hole is made in this insulating film 26 and an extraction electrode 27 is formed. Furthermore, a second insulating film 28 made of a BPSG film (borophosphosilicate glass) for planarization is deposited, and a contact hole is opened in this insulating film 28.
By forming the pixel electrode 29, a solid-state image sensor chip is created.

The configuration up to this point is the same as that of the conventional device, and the difference between the present device and this device lies in the order in which the transparent electrode and the light shield layer are formed on the photoconductive film 30. That is, on the photoconductive film 30, a light shield layer 41 made of a Ti thin film or the like and having a thickness of about 501) Oλ is formed, and this light shield layer 41 is etched away except for the optical black region.

A transparent electrode 42 made of ITO and having a thickness of approximately 500 mm is formed on the photoconductive film 30 and the light shield layer 41 exposed by removing the light shield layer 41.

Here, the formation process from the optical shield layer 41 to the transparent electrode 42 will be explained with reference to FIG. 3.

First, as shown in FIG. 3(a), a light shield layer 41 such as a Ti thin film is formed on the entire surface of the leading electric film 30 by vapor deposition or the like. The thickness of the light shield layer 41 is required to be 1000 Å or more in order to sufficiently shield light, and in this embodiment, the thickness is 500 Å or more.
The number was set to 0. Next, as shown in FIG. 3(b), a mask 43 is formed on the optical shield layer 41 over the optical black area. Next, an acid-based etching solution,
For example, using hydrochloric acid, the light shield layer 41 is selectively etched as shown in FIG. 3(C). At this time, the photoconductive film 3
Since 0 is hardly etched, the photoconductive film 30 is not damaged when the optical shield layer 41 is etched. Thereafter, the ITO electrode 42 is formed on the entire surface by vapor deposition or the like, thereby realizing the structure shown in FIG. 1.

Thus, according to this embodiment, since the optical shield layer 41 is formed before the ITO electrode 42 is formed, the ITO electrode 42 is not etched in the etching process when the optical shield layer 41 is formed. Therefore, a change in spectral sensitivity due to a change in film thickness during etching of the optical shield layer 41 of the ITO electrode 42, which has been a problem in the past, does not occur.

Therefore, by simply controlling the film thickness when forming the ITO electrode 42, the film thickness of the ITO electrode 42 can be optimally set, and optimal spectral sensitivity can be obtained with good reproducibility.

Further, since the optical shield layer 41 is etched by wet etching, side etching can be caused at the etched end of the optical shield layer 41, and the end can be formed into a tapered shape. The presence of this taber can prevent step breakage and film peeling of the ITO electrode 42 that will be formed later. Further, since the light shield layer 41 is a conductor, it goes without saying that a voltage is applied to the photoconductive film 30 in the optical black region.

FIG. 4 is a sectional view showing a schematic configuration of a second embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the previously described embodiments in that a transparent electrode is also present under the light shield layer. That is, in this embodiment, before forming the light shield layer 41, the first transparent electrode 42a made of ITO is formed on the photoconductive film 30 by vapor deposition or the like, and the light shield layer 41 made of Ti or the like is formed thereon. do. Next, as shown in FIG. 3, a mask is provided on the light shield layer 41, and the light shield layer 41 and the transparent electrode 42a are selectively etched.

Next, a second transparent electrode 42b made of ITO or the like is formed on the photoconductive film 30 and the light shield layer 41 exposed by etching.
is formed by vapor deposition or the like.

In such an embodiment, ITO is not present on the photoconductive film 30 not only in the image area other than the optical black area but also in the optical black area. There are four defendants. The reason for this structure is that if the signal in the optical black area changes due to the influence of the material of the film on the photoconductive film 30, the photoconductivity on the +11130 of the pixel between the optical black area and other areas will change. This is because the materials must be the same. If the signal in the optical black region does not change depending on the material of the film on the photoconductive film 30, such a configuration is not necessary. Further, the second transparent electrode 42b is formed after etching the light shield layer 41 as in the previous embodiment.

Therefore, the same effects as in the previous embodiment can be obtained.

FIG. 5 is a sectional view showing a schematic configuration of a third embodiment of the present invention. In FIG. 1, the same parts are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the previous first embodiment in that the light shield layer has a two-layer structure. That is, the optical shield layer 41 is the lower metal layer 41a.

It has a two-layer structure including an upper metal layer 41b, and the ends of these light shield layers 41 are formed into a gentle tapered shape. The reason why the ends of the optical shield layer 41 are tapered is to prevent breakage and film peeling at the ends of the ITO electrodes 42. In other words, ITO? If the M pole 42 breaks or peels off, it becomes impossible to uniformly apply the desired voltage to the entire photoconductive film 30, resulting in loss of uniformity in photosensitivity as a solid-state imaging device and defects in images. This results in problems such as the occurrence of

Specifically, first, the first light shield layer 41a is deposited on the light guide 'Ir5M30, and then the second light shield layer 41a is deposited on the light guide 'Ir5M30.
Defend b. The two light shield layers 41 thus formed are successively etched using the same etching solution and processed into a predetermined shape. In this case, if a material with a higher etching rate than the first optical shield layer 41a is used as the second front shield layer 41b, the end portion of the optical shield layer 41 will have a gentle tapered shape. For example, the first optical shield layer 41a is Mo, and the second optical shield layer 41
When b is Al1 and a phosphoric acid-based etching solution is used as the etching solution, the ends of the light shield layer 41 are reliably formed into a tapered shape. Thereafter, the structure shown in FIG. 5 is realized by forming a transparent electrode 42 made of ITO as in the previous embodiment.

Also in this embodiment, since the ITO m electrode 42 is formed after the optical shield layer 41, the film thickness of the ITO electrode 42 can be set optimally. Therefore, the first
The same effects as in the embodiment can be obtained. Furthermore, since the end of the optical shield layer 41 has a gentle tapered shape,
There is also the advantage that breakage and film peeling of the ITO electrode 42 at the end can be reliably prevented.

Note that the present invention is not limited to the embodiments described above. Although the embodiment has been described using a CCD type imaging device using a charge transfer section, the present invention can also be applied to a MOS type imaging device.

Furthermore, the material of the optical shield layer is not limited to Ti.
Any material is sufficient as long as it is conductive and blocks light; A, Q
, Cr, Mo, W, etc., or metal silicide can also be used. Furthermore, the film thicknesses of the light shield layer and the transparent electrode can be changed as appropriate depending on specifications.

In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, since the transparent electrode is formed on the light shield layer which is patterned by etching, the transparent electrode is not etched when the light shield layer is etched. It is possible to prevent this from happening. Therefore, the film thickness of the transparent electrode can be prevented from changing and the film thickness of the transparent electrode can be optimally set, and the spectral sensitivity can be adjusted to the optimal sensitivity with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a schematic configuration of a stacked solid-state imaging device according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view showing an enlarged configuration of one pixel of the device, and FIG. A cross-sectional view showing the formation process of a light shield layer and a transparent electrode in the device,
FIG. 4 is a cross-sectional view showing a schematic configuration of a second embodiment of the present invention, FIG. 5 is a cross-sectional view showing a schematic configuration of a third embodiment of the present invention, and FIG. It is a sectional view for explanation. 10... St substrate, 20... Chip element, 21...
・Element isolation layer, 22... CCD channel, 23...
Storage diode, 24.25... Transfer gate, 26°28... Insulating film, 27... Extraction electrode, 29...
Pixel electrode, 30.31, 32.33... photoconductive film, 4
1.41a, 41b--light shield layer, 42°42a
, 42b...Transparent electrode, 43...Mask. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Cause 3 Figure 2

Claims (5)

[Claims] (1) A solid-state image sensor chip in which a signal charge storage section and a signal charge readout section are formed on a semiconductor substrate, and a pixel electrode electrically connected to the signal charge storage section is formed on the top thereof, and this solid-state image sensor chip. A photoconductive film laminated on the element chip, a conductive light shield layer formed on the optical black area on the photoconductive film, and a transparent electrode formed on the photoconductive film and the light shield layer. A stacked solid-state imaging device comprising: (2) The stacked solid-state imaging device according to claim 1, wherein the light shield layer has a two-layer structure made of different materials, and an end portion of the light shield layer is formed in a tapered shape. (3) A photoelectric conversion device is mounted on a solid-state image sensor chip in which a signal charge storage section and a signal charge readout section are formed on a semiconductor substrate, and a pixel electrode electrically connected to the signal charge storage section is formed on top of the signal charge storage section and a signal charge readout section. a step of laminating a photoconductive film as a part, a step of forming a conductive light shield layer on the photoconductive film, and a step of etching away the light shield layer except on the optical black region of the photoconductive film. A method for manufacturing a stacked solid-state imaging device, comprising the steps of: forming a transparent electrode on the photoconductive film and the light shield layer. (4) A photoelectric conversion device is mounted on a solid-state image sensor chip in which a signal charge storage section and a signal charge readout section are formed on a semiconductor substrate, and a pixel electrode electrically connected to the signal charge storage section is formed on top of the signal charge storage section and a signal charge readout section. a step of laminating a photoconductive film as a part; a step of forming a first transparent electrode on the photoconductive film;
forming a light shield layer on the first transparent electrode; etching away the light shield layer and the first transparent electrode except on the optical black region of the photoconductive film; A method for manufacturing a stacked solid-state imaging device, comprising the step of forming a second transparent electrode on the film and the light shield layer. (5) The light shield layer is formed in a two-layer structure made of different materials, and an etchant that etches the upper layer faster than the lower layer is used during the etching. 5. The method for manufacturing a stacked solid-state imaging device according to 3 or 4.