JPS59196667A - Solid-state image pickup device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a solid-state imaging device, and particularly to a solid-state imaging device having a function of suppressing a pluming phenomenon and a smear phenomenon.

[Technical background of the invention and its problems]

2. Description of the Related Art Conventionally, as a solid-state imaging device, such as an interline transfer type image sensor, the one shown in FIG. 1 is known.

1 in the figure is, for example, a p-type semiconductor substrate.

Near the center of the housing part of the substrate 1, an n+ type semiconductor region (photosensitive part) 2 is formed for accumulating the signal d generated by the incidence of light. Further, on the surface of the substrate 1,
An i-type buried region 3 forming a part of the vertical shift resistor (1 to 1) is formed in the vicinity of said 1(& tip 2().Furthermore, on the surface of said substrate 1, a part of the vertical shift resistor is formed. An n+10-shaped overflow drain region (0, F, D region) 4 discharges excess charges generated in the photosensitive section 2,
It is formed close to the photosensitive section 2.

Furthermore, on the absorption surface of the substrate 1, the photosensitive portion 2.0, I
', nj 5 is provided so as to be located between D areas 4,
and a p+ type channel blocking region 6 surrounding the photosensitive section 2.
is provided. An insulating film 7 is coated on the substrate 1 including the photosensitive section 2 and the like. In this insulating film 7, first layer transfer electrodes 81r82 of different pixels are provided, and furthermore, a second layer transfer electrode 9 to be paired with the transfer electrode 81 is provided. Note that the transfer electrode 819 serves as an exposed portion for reading out the signal charges accumulated in the photosensitive portion 2. On the insulating film 7 is a light shielding film 1 made of, for example, At and having an opening window 10 in a portion corresponding to the photosensitive portion 2.
1 is provided. Absolute radius including this light shield film 11
A protective film 12 is provided on the film z.

However, in the image sensor having the above structure, since O, F, and D regions 4 are provided on the surface of the substrate 1 to suppress the blooming phenomenon, the pixel size is 2/3 inch,
When the size gradually decreased to 1/2 inch and 8 rpm, there was a limit to high integration in the horizontal direction. As a result, there has been a problem that the readout means for both threads and signal charges cannot be highly integrated, and the resolution of the image sensor cannot be improved satisfactorily.

In addition, since the long wavelength component of the incident light incident on the photosensitive section 2 is photoelectrically converted deep within the substrate 1, the generated charge is 1iJ4? O enters the embedded area of the vertical shift register and causes a smear phenomenon.For this reason, an image sensor shown in FIG. 2 has been known. 21 in the figure is, for example, an n-type semiconductor substrate. A shallow P-well region 22 and a deep P-well region 23 are formed on the surface of the substrate 1, respectively.

On the surface of the shallow P-well region 22, the layered semiconductor region (photosensitive portion) 2 described above is provided.

On the other hand, on the surface of the deep P-well region 23, a layered buried region 3 and a p+ type channel blocking region 6 are provided. On the P-well regions 22 and 23, a first
Layer transfer electrode 81.

82, an insulating film 7 having a second layer of transfer electrodes 9 at a predetermined distance is provided. Furthermore, on this insulating film 7,
A light shield film 11 and a protective film 12 are provided.

The above-described image cell shown in FIG. 21 side (blooming phenomenon suppression function), and by providing the P-well region 22, long wavelength light is excluded to the substrate 21 (smear phenomenon suppression function). However, in the image cell described above, the P-well regions 22 and 23 are usually formed by ion implantation of impurities into the surface of the substrate 21 and heat treatment. When the pixel size becomes smaller as a result of heat treatment and the pixel size becomes smaller, a shallow P as shown in Figure 2
- It becomes difficult to form the well region 22.

In such a case, a function to suppress the blooming phenomenon cannot be obtained. Therefore, the above-mentioned problems shown in FIG. 1 have not been solved.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solid-state imaging device that can suppress blooming and smear phenomena and improve resolution.

[Summary of the invention]

The present invention provides a first conductivity type drain region on the surface of a first conductivity type semiconductor substrate from which excess charges are discharged, a semiconductor single crystal is provided on the substrate including this drain region, and the single crystal A second conductivity type semiconductor region for storing signal charges generated by light incidence on the surface thereof is provided above the drain region, and a readout means for sequentially reading out the signal charges stored in the semiconductor region. Will blooming or smearing occur? It is possible to suppress this and improve resolution.

EXAMPLE Hereinafter, an incline transfer type image sensor which is an example of the present invention will be described with reference to the manufacturing method shown in FIGS. 3(a) to (C), FIGS. 4 and 5.

[1] First, an n-type impurity, such as arsenic, was ion-implanted into a portion of the surface of the p-type St substrate 31 located below where the photosensitive portion was to be formed, and an n-thousand-type drain region 32 was formed by heat treatment. . Subsequently, a p-type single crystal silicon layer 33 was formed on the substrate 31 including the drain region 32 by an epitaxial method (as shown in FIG. 3(-)). Next, on the surface of this silicon layer 33, an n medium-sized semiconductor region (photosensitive section) 34 that accumulates signal charges generated by light incidence by a conventional method, and a part of a vertical shift register near this photosensitive section 34 is formed. An n+ type buried region 35, a p+ type channel blocking region 36, and an n medium layer (not shown) connected to the drain region 32 were formed (as shown in FIG. 3(b)).

Note that the area of the photosensitive portion 340 is smaller than the area of the drain region 32.

[11] Next, the silicon layer 33 including the photosensitive portion 34 etc.
A first-layer transfer electrode 381.3 made of, for example, polycrystalline silicon is applied thereon via a first insulating layer 371 using a conventional method.
82 was established. Subsequently, a second layer of transfer electrodes 39 was formed via the second insulating film 372 and gold. Next, a third insulating film 373 is formed on the insulating film 372 including the transfer electrode 39.
was formed. Hereinafter, the first to third insulating films 371 to 3
73 will be collectively referred to simply as an insulating film 4o. Furthermore, after forming a contact portion 42 in a portion of this insulating film 4o corresponding to the layered layer 4, At was deposited on the entire surface. After that,
By patterning, an opening window 43 is formed in a portion corresponding to the photosensitive portion 34, and the contact portion 42 is formed by patterning.
A light shield film 44 was formed to be connected to the i-type layer 41 via the . Note that a constant DC current is applied to the drain region 32 through the light shield film 44 . Continuing,
Phosphorus is formed as a protective film on the insulating film 4θ including the light shield film 44.

A silicate glass film (PSG film) 45 was formed to manufacture an interline transfer type image sensor (Fig. 3(C),
(Illustrated in Figures 4 and 5). In addition, Figure 4 is Figure 3(c)
46 in FIG. 4 are vertical shift renostars, and 47 are pixels. Further, FIG. 5 shows an enlarged sectional view taken along the line XX in FIG. 4.

As shown in FIGS. 3(C), 4, and 5, the image sensor of the present invention includes an n-core type drain region 32 provided on the surface of a p-type St substrate 31. A p-type single-crystal silicon layer 33 is provided on a substrate 31, an n-medium-sized photosensitive portion 34 is provided on the surface of this silicon layer 33 so as to be located above the front self-drain region 32, and a It has a structure in which an i-type buried region 35 is provided on the surface of the single crystal layer 31.

In an image sensor having such a structure, the excess electric current W generated in the photosensitive section 34 can be removed to the drain region 32 by applying a constant positive voltage to the light shielding film 44 connected to the drain region 32, thereby causing a blooming phenomenon. The occurrence of smear phenomenon can be avoided. FIG. 6 is a characteristic diagram showing the potential curve of the image sensor measured along the depth direction of the photosensitive portion 34, and () in the figure indicates the potential curve of the photosensitive portion 34.
4, (a) shows the potential curve in the single crystal silicon layer 33, (b) shows the potential curve in the drain region 32, and (b) shows the potential curve in the St substrate 3, respectively. From the same figure, the charge generated in the photosensitive section 34 is normally expressed by the potential curve (7).
However, if the charge is excessively large, it will exceed the potential peak point of the tU potential curve a) and be sent to the drain region 32 in the right direction.
can. Also, even if a long wavelength comes in, the generated 1
The load is dumped into the drain area.

Furthermore, unlike the conventional image sensor shown in FIG. 1, there is no need to provide O, F, and D regions on the substrate surface for the purpose of discharging excessive loads, so higher integration in the horizontal direction can be achieved compared to the conventional image sensor. , the resolution of the image sensor can be improved by arranging more photosensitive pixels.

In addition, in the above embodiment, the conductor of the Si plate, the photosensitive area, etc.
The I8 type is not limited to the above-mentioned case, but may also be the opposite -h'ton type.

Further, in the above embodiment, the solid-state imaging device i'e is an interline transfer type image sensor (area image sensor), but the present invention is not limited to this and can be applied to a linear image sensor.

〔Effect of the invention〕

As detailed above, according to the present invention, the blooming phenomenon,
It is possible to provide an all-in-one imaging device such as an interline transfer type image sensor that can suppress smear plates and improve resolution.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional incline transfer type image sensor, Fig. 2 is a sectional view of another conventional interline transfer type image sensor, and Figs. 3(a) to 3(c) are one embodiment of the present invention. A top view showing an example of an interline transfer type image sensor in manufacturing process 11, FIG. 4 is a reduced plan view of FIG. 3(c), and FIG. 5 is an enlarged view taken along the line X-X of FIG. 4. Cross-sections 1 and 6 are characteristic diagrams showing the first-position curve in the closing direction of the photosensitive portion of the image sensor shown in FIGS. 3(C), 4, and 5. 31... p-type St substrate, 32... n++-type drain region, 33... p-type single crystal shoddy layer, 34...
... n+ type semiconductor region (photosensitive part), 35... n+ type buried region, 36... p+ type channel blocking region,
371-373.40... Insulation J true 1.3B. 382.39... Transfer electrode, 41... Gauge layer, 42
...Contact part, 43...Opening hole 1? μ, 44...
- Optical roll film, 45... PSG film, 46... Vertical shift renostar, 47... Pixel. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 0 Figure 2 0 Figure 3 Figure 5 Figure 6 - 405-

Claims (1)

[Claims] a semiconductor substrate of a first conductivity type; a drain region of a second conductivity type provided on the surface of the substrate and from which excess charge is discharged;
A semiconductor single crystal layer provided on the substrate including this drain region, and a semiconductor single crystal layer provided on the surface of this single crystal layer located above the drain region to accumulate a signal tE charge generated (by light incidence). What is claimed is: 1. A solid-body imaging device comprising: a semiconductor region of a second conductivity type; and readout means for sequentially reading out signal charges accumulated in the semiconductor region.