JPS5815280A - solid-state image sensor - 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 The present invention relates to a solid-state image sensor, and particularly to a solid-state image sensor that can increase the sensitivity of a light receiving section.

Conventionally, a light receiving section in a solid-state image sensor usually uses a pn junction because it has a high quantum efficiency and can have a large charge storage capacity. Common methods for forming a p-n junction include, for example, a method of thermally diffusing a donor into a P-type semiconductor substrate and a method of ion implantation. The p-n junction formed by thermal diffusion becomes almost a step junction on one side, and the depletion layer only spreads toward the substrate side, and the p-n junction is formed relatively deep, so the light at the surface of the substrate is On the other hand, in the case of a p-n junction formed by ion implantation, the depth is shallow and the amount of implanted impurities is reduced by heating. The depletion layer reaches the substrate surface and the photogenerated carriers generated on the substrate surface can be accumulated in the depletion layer because the depletion layer cannot be formed in large numbers due to diffusion. The primary carrier is lost due to degregation or recombination, and in this case as well, no improvement in sensitivity can be expected.An object of the present invention is to obtain a solid-state imaging device with a high sensitivity of the light-receiving section.

The present invention provides a solid-state imaging device having a light receiving section formed on a surface of a conductive type semiconductor substrate and having a portion in contact with a high concentration conductive type channel stopper region, wherein the light receiving section is in contact with at least the channel stopper region. one conductivity type region;
A solid-state imaging device is obtained, which includes a region of the other conductivity type forming a junction with the region of the negative conductivity type.

That is, according to the present invention, two pn junctions are sequentially arranged in the light receiving section for incident light, and the sensitivity is increased by accumulating photogenerated carriers only in the middle region of the two pn junctions. To obtain a solid-state image sensor that can be increased in size.

Next, the present invention will be explained in more detail using the drawings.

FIG. 1 is a cross-sectional view of a solid-state imaging device showing an embodiment of the present invention, in which %l is a P-type semiconductor substrate, 2 is a P+ lid channel stopper, 3 is a field oxide film, and 4 is a gate oxide film%5 and 6. are the n-type region and the P-type head region, respectively. The n-type region 5 and the P-type head region 6 form a light receiving section together with the P-type substrate 1, and the P-type head region 6 is continuous with the channel stopper 2. 7
is an n-type region, which receives carriers from the light receiving section,
Output circuit (not shown) by charge multiplexing means (not shown)
It is used to send electric charges to. Reference numeral 8 denotes a transfer gate electrode for sending carriers from the light receiving section to the n-type region 7.

To explain this structure specifically, if the impurity concentration of the P-type substrate 1 is lXl0''cm=, the channel stopper 2
is energy 100 keV, dose so 2~3 x 10 days C1
Formed by n-2 boron ion implantation, the field oxide film 3 has a thickness of about 1000" in wet O7.
．． A layer of about 2μ ijK is formed using a conventional selective oxidation technique. Next, the n-type regions 5 and 7 are given an energy of 170 key,
After forming by phosphorus ion implantation at a dose of t1.4×1oItα2, heat treatment is performed in nitrogen at 1150° C. for about 2 hours to push phosphorus to a depth of about 1.2 μm from the surface. After a long time, the gate oxide film 4 was reduced to a thickness of 100A by normal thermal oxidation.
After forming the gate electrode 8, a gate electrode 8 is formed of phosphorus-doped polycrystalline silicon. Finally, poron ion implantation with 1 energy of 5okev and a dose of lX1011cIfLl is performed only in the light receiving portion to form a P-type head region 6. At this time, it is made to be continuous with the P-type substrate 1. The energy diagram of the light-receiving section made in this way is the same as that shown in FIG. 9 and 10 are p-N
0, which is a junction. Now, if 8V is applied to the gate electrode,
Since its surface potential is approximately 8V, the depletion layer extending from the p-N junction 10 to the P-type substrate 1 is approximately 3μ, which is approximately 70V.
It is possible to detect wavelengths up to 001. Also,
Since the depletion layer of the n-type region 5 also extends to the surface, the generated carriers on the short wavelength side are of course also accumulated in the nm region 5, and at the same time, the carriers accumulated in the n-type region 5 are transferred to the P-type region 9 by 8i0. Since it is separated from the -8i interface, it is possible to prevent trauma, damage, and recombination due to surface states.

Further, since holes in the valence band of the n-type region 5 are also extracted to the substrate 1 by the P-type head region 6, the probability of inter-band recombination can be reduced.

From the above, the sensitivity of the solid-state image sensor according to the present invention is much higher than that of the conventional one.Furthermore, the charge storage capacity of the light receiving section is
Since it is the sum of the respective capacitances of the p-N junctions 9 and 10, it can be made larger than the conventional one.

Finally, it goes without saying that the present invention is applicable regardless of whether the solid-state imaging device is a CCD type or a MOS type.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a solid-state image element #1 showing an embodiment of the present invention, and FIG. 2 is a band energy diagram of a light receiving section.

Claims (1)

[Claims] Formed on the surface of a semiconductor substrate of one conductivity type, with a part of it being highly concentrated.
In a solid-state imaging device having a light receiving part in contact with a conductivity type channel stopper region, the light receiving part has at least a region of one conductivity type in contact with the channel stopper region and a region of another conductivity type forming a junction with the -conductivity type region. A solid-state image sensor comprising: