JPS5860568A - Semiconductor image-pickup device - Google Patents

Abstract

PURPOSE:To improve the light detecting sensitivity of the titled device by a method wherein a V-groove structure is formed at the light-receiving section of a photosensor, and the depletion layer width of a P-N junction is effectively utilized. CONSTITUTION:Using the patternized insulation oxide film 2 as an etching mask, a V-groove 1a is formed by performing an anisotropic etching on the surface of a P type semiconductor substrate 1, and at the same time, an N type region 4a is formed by ion-implating an AS, for example, as shallow as possible as impurities from the surface of an N-groove 1a. As for each P-N junction of a for each P-N junction of a source section 3 and a drain section 8 to be used for light receiving, when a gate section 6 is in OFF position and light 11 of certain wavelength region is irradiated on the N type region 4a of the source 3 to be used for light receiving, the light 11 is irradiated from oblique direction to the depletion layer 12a of the P-N junction, and at the same time, the light 11a which was reflectedon the surface simultaneously with the light 11 is irradiated from the oblique direction on the depletion layer 12a from the surface on the opposite side in the same manner as above, light 12 and reflected light 11a are absorbed into the depletion region 12a, a pair of electron 13 and a hole 14 is formed, the electron 13 and the hole 14 moves to an N type region 4a and a P type region respectively, thereby enabling to reduce the inverted bias potential difference of the source section 3.

Description

[Detailed description of the invention] The present invention relates to a semiconductor imaging device.

In recent years, as manufacturing technology for semiconductor integrated circuits has improved, semiconductor sensors have also been integrated using this technology, and semiconductor imaging devices have been developed that are provided with a detection signal processing function.

As a conventional ovao device, the optical sensor part uses a photodiode to perform photoelectric conversion processing.
O! There is an all-imaging device, which is shown in FIG. That is, in this FIG. 1, (11 is a P-type semiconductor group I11, (23 is a group 1m): nine insulating oxide scales selectively patterned, and (3) is an N layer formed by diffusion on the substrate surface. a source section comprising a shadow region (4) and its electrode (5) and forming a photodiode of the optical sensor section;
(9 is a gate portion having an electrode (7), and 2 is a drain portion consisting of an N shadow region (9) similarly diffused on the substrate surface and its electrode Ql.

In this conventional structure, the PN junction in the source part (dan) is
Normally, it is reverse biased to the same potential as the PN junction of the drain (diameter), and otherwise uses the operating principle of a general MO8 type transistor.

Therefore, when the gate part is in the OFF state, when the light receiving N-type source region (4) is irradiated with light in a certain wavelength range, the source of this light is in the PN junction O depletion layer Q2. As described above, since this PN junction is reverse biased, the generated electrons α3 are absorbed in the FiN type region.

The holes α4 move to the P shadow region of the substrate, and the reverse bias potential difference becomes smaller. Then, the gate part (al electrode (7)
When a 4C voltage is applied and it turns on, there is an N voltage directly below the gate.
When a shaped channel occurs, IEjl between the source and drain
A current flows after IIa, and the source portion (Dan) is returned to its old reverse biased potential.

Therefore, the amount of charge obtained by integrating this current can be seen as a detection signal photoelectrically converted corresponding to the initial amount of incident light Ql.

However, in conventional devices of this type, the width of the depletion layer (2) of the PN junction in the source section (1), which is involved in the absorption of light aυ, is effectively utilized, but if you try to design the width to be large, , there was a problem in that it was limited by the impurity content of the semiconductor substrate (11).

In view of these conventional problems, the present invention adopts a KV groove structure in the light receiving part of an optical sensor, forms a photodiode within the structure, and utilizes it for the depletion layer width \c1ir effect of the PN junction. This is intended to improve the detection sensitivity.

Hereinafter, one embodiment of the inventive device will be explained in detail with reference to FIG. 112.

In the embodiment shown in FIG. 2, the same reference numerals as in the conventional example shown in FIG. Configure. That is, patterned insulating oxide II
(Use 21 as an etching mask, P-type conductor substrate (1)
) is immersed in, for example, a KOH solution and anisotropically etched to form a V-groove (]a).
Groove 1a) In this method, ion implantation of, for example, mu 8 as an impurity is performed as shallowly as possible to form the N shadow region (4a).
This N shadow region (4a) constitutes a source ill (3) which becomes a Fi photodiode, and at the same time an N shadow region (9) of drain portion diameter) is also formed in the self-line.

Therefore this 5! The embodiment device also utilizes the operating principle of MOg type transistors. First, each PN junction between the light receiving source part (blade and drain part diameter) is connected to the same potential with the same potential. diameter) of N shadow areas (
When 4a) is irradiated with light 0υ in a certain wavelength range, since the same region (41) is formed in the shape of a V-groove (1a), this light I will penetrate into the depletion layer (12m) of the PN junction. At the same time, the particles (11m) reflected by the surface are also incident obliquely into the depletion layer (12a) from the opposite surface, and in this way the depletion layer (12a) is In the area of the layer (12 m), the original α2. and reflected light (l
1m) is absorbed to generate electron αj and hole 04 pairs,
Moreover, the electron a3 moves to the N shadow region (4a) and the hole α◆ moves to the P shadow region of the substrate (1), resulting in the source l!
The reverse bias potential difference of 1131 becomes smaller. Then, while this situation continues, a voltage is applied to the gate electrode (7) to turn it on, and if an N-type ≠ layer occurs directly under this gate, a short circuit will occur between the source and drain. A current flows through the source section (31), and the source section (31) is restored to its old reverse-biased potential. Therefore, as in the conventional example, the incident amount can be detected from the amount of charge obtained by integrating this current. .

In the above embodiment, the conductive type of the substrate is t-P type, but it may be of N type, and it goes without saying that a Schottky diode other than the optical sensor 1iK7 autodiode may be used.

As detailed above, according to the present invention, since the light receiving 5t-V groove structure of the original sensor is used, the detected light is incident on the depletion layer of the PN junction from an oblique direction, and the original light reflected on the light receiving surface is also Similarly, since the depletion layer is incident on the opposite surface from an oblique direction, the width of the depletion layer can be effectively used without being restricted by the impurity concentration of the substrate, and the original detection level can be reduced. Furthermore, the detection sensitivity can be improved, and the structure is simple and can be implemented easily and inexpensively.

[Brief explanation of the drawing]

FIG. 1 shows a general configuration V of a conventional semiconductor imaging device.
FIG. 2 is a schematic diagram showing a semiconductor imaging device according to an embodiment of the present invention. (1)...P-type semiconductor substrate, (11)...V groove, (21...insulating oxide film, (side...source part,
(4). (4a)...N shadow area, (5)...electrode, (9
...Gate part, (7) "...φ electrode, (shadow...
-Drain part, (9)-...N shadow area, (lG...
・Electrode, aυ...Incidence amount, (l1m)...Reflected light, Q3゜(12m)...Depletion layer.

Claims (1)

[Claims] A semiconductor imaging device characterized in that a light receiving section of a semiconductor sensor has a V-groove structure, and incident light and reflected light from the light receiving section are made to enter the light receiving section from oblique directions.