JPS593068B2 - solid-state image sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-sensitivity, high-density solid-state imaging device having a photoconductor film.

As shown in FIG. 1A, a top view, and FIG. A picture element part 2 (described later) is provided, and this picture element part 2
A driving section 3 such as a shift register is provided around the pixel section 3 to drive the picture element section.

Note that an insulator is formed on the drive section 3. A metal wiring 5 is provided which is connected to the terminal of the drive part 3 through an opening 5 in the insulating film and extends to the external wiring pad part 4.
Furthermore, a photoconductive film (ZnSe-Znl-xC
dxTe) 6 and a transparent electrode T are provided respectively.
Now, in the process of manufacturing the above-described solid-state image sensor, after forming the picture element part 2, the driving part 3, and the metal wiring 5 on the base substrate 1, the photoconductive film 6 is formed. When attaching the photoconductive film 6 to the base substrate 1, the photolithographic method used in the manufacture of general semiconductor devices cannot be used because it is a wet method and the photoconductive properties of the photoconductive film 6 deteriorate. A method (referred to as a mask vapor deposition method) is used in which the formed metal wiring 5 of the drive section 3 is covered with a vapor deposition mask, and the photoconductive film 6 and the transparent electrode 7 are vapor deposited on the picture element section 2.

However, when using the mask evaporation method, the 20 mask alignment accuracy is very poor, on the order of several hundred microns. As shown, if the photoconductive film 6 or the transparent electrode T attached thereon is significantly deviated from the predetermined position, the metal wiring on the drive section 3 ( For example, cracks A may occur in the photoconductive film 6 overlapping the Al wiring (5), and dark current increases at the cracks A. Furthermore, if the transparent electrode T is misaligned, there is a risk that a short circuit B will occur between the metal wirings 5. In order to eliminate defects such as 30 or more, the conventional method solves the problem by increasing the tolerance range A of misalignment.

However, the method of increasing the tolerance range A for misalignment has the disadvantage that the chip size of the solid-state imaging device becomes extremely large. The present invention aims to reduce the occurrence of defects due to misalignment of the mask during formation of the photoconductive film by covering the metal wiring provided around the picture element with an insulating film having a coefficient of linear expansion similar to that of the photoconductive film. That is.

The present invention will be described below with reference to the drawings and embodiments. FIG. 3 is a sectional view showing one embodiment of the present invention.

On a silicon substrate 11, a photodiode for sensing an optical image, a picture element section 12 consisting of a BBD element, and a driving section 13 consisting of a shift register etc. constituted by a MOS element etc. were formed using a normal MOS process. After, the above B
The insulating film 16 is removed except for the pad portion 15 of the metal wiring 14 from which the electrodes of the pixel portion 12 and drive circuit portion 13 of the BD element are taken out.
has been formed. At this time, if the linear expansion coefficient of the photoconductive film to be formed in a later step is significantly different from that of the insulating film 16, for example, ZnSe-Znl-X may be used as the photoconductive film.
When CdxTe is used and SiO2 is used as the insulating film by the usual CVD method or PVD method, ZnSe
-Linear expansion coefficient of Znl-XCdxTe (70-80×1
0-7Deg-1), the linear expansion coefficient of SiO2 (
5x10-7Deg-1) is very small, so SiO
Cracks occur in the ZnSe-Znl-XCdxTe film at the overlapped portions as in the prior art. Therefore, when using ZnSe-Znl-XCdxTe as a photoconductive film, an insulating film with a linear expansion coefficient of about 20 to 130 x 10-7 Deg-1, for example, Si3N4 (39 x 10-7),
Al2O3 (70×10-7Deg-1), 10-20
Phosphorous glass containing %P2O5 (approximately 50 x 10-7Deg
-1), SiO (40×10 −7 Deg), etc. must be used. By the way, the picture element part 12 and the pad part 15
As a method for removing the insulating film 16, as shown in FIGS.
After covering the picture element part 12 and pad part 15 in step 7, PVD
An insulating film 16 is deposited over the entire surface using a method or a CVD method (FIG. 4a).

Thereafter, the insulating film 16 on the etching preventive film 17 is removed by etching using a photoresist pattern 18 having an inverse pattern of the etching preventive film 17 by photoetching method 1, thereby forming the insulating film 16.

At this time, P2O was used as the insulating film by CVD method.
If phosphorus glass with a concentration of 10 to 20% is deposited or Al2O3 or Si3N4 is deposited by sputtering, a conventional photoresist pattern with a thickness of 1 to 2 microns can be used as an anti-etching film. Further, when a photoresist pattern is used as an etching prevention film, edge flow of the resist pattern can be prevented by using an inert gas plasma such as N2 or Ar2 for post-baking (FIG. 4b). Next, the resist pattern 18 used for etching and the etching prevention film 1 are
By removing 7, the device shown in FIG. 3 is obtained. In addition, if a resist pattern is used as the etching prevention film at this time, even if it is slightly carbonized,
There is an advantage that the resist pattern used for etching can be removed by etching at the same time using 02 plasma. When connecting the photodiodes of the picture element section 12 and the photoconductive film, a contact window (not shown) is opened in the insulator on each photodiode of the picture element section 12 using photolithography.
After forming an O electrode in the opening (not shown), a photoconductive film 19 and a transparent electrode 20 are sequentially deposited using a vapor deposition mask, thereby producing a solid-state image sensor with a photoconductive film shown in FIG. An element is obtained.

Note that here, the step of opening a contact window in the insulator of the photodiode may be performed before the step of forming the insulating film 16. As described above, in the present invention, since the metal wire portion 14 is covered with the insulating film 16 having the same expansion coefficient as the photoconductive film 19, even if one photoconductive film 16 overlaps the metal wiring portion 14, the expansion coefficient is There will be no cracking or peeling due to differences in
No leakage current occurs in the photoconductive film 16.

Since the two metal wirings 14 are covered with the insulating film 16, misalignment of the transparent electrodes 20 occurs, and the transparent electrodes 20 are covered with the metal wirings 14.
A short circuit between the wiring lines 14 does not occur even if the wires are connected to the top.

3. Even if there is some misalignment of the metal mask, there will be no problem of scratching of the photoconductive film 16 or shorting between the wiring lines 14, so there is no need to take a wide misalignment tolerance range B shown in FIG. The area can be reduced, making it suitable for high integration.

Since areas other than the four picture element parts 12 can be covered with the photoconductive film 19, the photoconductive film 19 can also be used as a light shielding film for the drive part 13 having a shift register or other active elements.

5. By covering the picture element part 12 and the pad part 15 with the etching prevention film 17 in advance in the step of forming the insulating film 16, the picture element part is not attacked by the etching solution, so that the solid-state image sensor can be manufactured with high yield. Can be formed.

It has the following effects.

Here, an enlarged sectional view of a part C of the picture element section 12 in the sectional view of FIG. 5 is shown in FIG. 6a, a plan view thereof shown in FIG. 6b, and an operation diagram shown in FIGS. The structure and operation of the picture element section will be explained using the following.

First, in FIGS. 6A and 6B, the n+ type diffusion region 21 is P
A mold substrate 11 and a photodiode are formed. n+ area 22
is a diffusion region constituting the BBD, and is a region where charge charges are transferred from the n+ region 21 by applying a voltage to the first gate electrode 23. 24 and 25 are insulators, respectively.

The electrode 26 is made of MO, is electrically connected to the n+ region 21, and also serves as an electrode of the hole blocking layer 27. The second gate electrode 28 constitutes the gate of the BBD. Now,
The optical information reading operation of the solid-state image sensor shown in FIGS. 6A and 6B will be explained using FIGS. 7A and 7B.

Figure 6a shows the pulse pattern for driving this element.
shows the potential change in the n+ region 21.

When a read pulse VCH is applied to the first gate electrode 23 at time t, the potential in the region 21 changes as shown in FIG.
It is charged to (VCH-VT) as shown in FIG. Here, VT is the n+ region 21, 22 and the first gate electrode 23.
This is the threshold voltage of the FET consisting of Now, when there is incident light, electron-hole pairs are generated in the photoconductor 19, which reach the electrodes 26 and 20, respectively, and the potential of the electrode 26, that is, the region 21, decreases. This potential drop is proportional to the amount of incident light, and is accumulated for one field period, so that the potential decreases to VS. Furthermore, at time T2, VC is applied to the first gate electrode 23.
When H is applied, the surface potential of the underlying semiconductor substrate 11 increases, and as a result, electrons are transferred from n+ region 21 to n+ region 22. As a result, the potential of n+ region 21 rises again and becomes (CH-T). Therefore, n+ region 2
The total amount of charge transferred to 2 corresponds to the illuminance of the incident light. In this way, the optical information read into the n+ region 22 is
By applying the transfer pulse shown in Figure a to the second gate electrode 28, optical information is transferred in the vertical direction of the paper in the form of BBD charge transfer.

That is, the signal photoelectrically converted by the photodiode can be sent to the output stage as a two-phase clock signal. As described above, since the metal wiring on the drive part is covered with an insulating film, the present invention not only prevents short circuits between the metal wiring due to misalignment of transparent electrodes, etc., but also - allows the pixel part and the metal wiring to be narrowed. This has the effect of facilitating the highly integrated configuration of solid-state imaging devices.

[Brief explanation of the drawing]

FIGS. 1A and 1B are a plan view and a cross-sectional view of a solid-state image sensor having a photoconductive film, and FIG.
3 and 5 are cross-sectional views showing one embodiment of the solid-state imaging device of the present invention, FIGS. 4A and 4B are manufacturing process diagrams of the same embodiment, and FIGS.
Figures A and b are an enlarged sectional view and a plan view of the main parts of the same embodiment, and
Figures A and b are explanatory diagrams of the operation of the same embodiment. 11... Semiconductor substrate, 12... Picture element section, 13... Drive section, 14... Metal wiring, 15... Electrode pad Part 16...Insulating film having a tensile coefficient similar to that of the photoconductive film, 17...
...Etching prevention film, 18...Photoresist pattern, 19...Photoconductive film, 20...
・Transparent electrode, 21, 22...n+ diffusion layer, 23
, 28... gate electrode, 24, 25...
- Insulating film, 26... electrode, 27... hole blocking layer.

Claims (1)

[Scope of Claims] 1. A picture element section that senses and transfers an optical image, a photoconductive film connected and formed on the sensing section of the picture element section, and a drive circuit section that drives the picture element section; It has a conductor wiring that connects the drive circuit section and an external connection pad electrode, and is characterized in that an insulator having approximately the same expansion coefficient as the photoconductive film is formed on the conductor wiring. Solid-state image sensor. 2. The solid-state image pickup device according to claim 1, wherein a photoconductive film is formed on the drive circuit portion with an insulating material interposed therebetween.