JPS60187053A - Ccd type solid-state image pickup element - Google Patents

Abstract

PURPOSE:To enable to obtain a large junction capacitance by a method wherein a high density p type region is formed under an n type diffusion layer which constitutes a light-receiving diode. CONSTITUTION:An n type diffusion layer 3 whereon a photodiode will be formed, an n-well whereon the transfer gate of CCD will be formed, a transfer gate 6 and a shifting gate 7 are formed on a p type Si substrate 1. Under said layer 3, a p type region 8 having the density higher than that of the substrate 1 is formed. When the density of the region 8 is brought to 5X10<16>cm<-3> or thereabout, for example, the value of the junction capacitance of the photodiode of the above-mentioned structure becomes 7X10<4>PF/cm<-3>, and the quantity of saturated charge is made larger. As a result, the quantity of saturated light is also made larger, thereby enabling to make the dynamic range larger.

Description

[Detailed Description of the Invention] [Technical Field] The present invention consists of a light receiving element consisting of a photodiode, a scanning circuit consisting of a charge transfer device (aOD), and a transfer gate that transfers a signal from the light receiving element to the scanning circuit. The present invention relates to a so-called CCD type solid-state image sensor, and relates to the structure of its light receiving section.

[Prior art]

FIG. 1 shows a cross-sectional view of a conventional CCD type solid-state image sensor. (1) is a P-type S1 substrate, and (2) is an insulating film formed on the surface, which is usually a thermal oxide film. (3) is an N-type diffusion layer forming a photodiode.

(4) is a junction capacitance formed by (8) and (1), and signal charges are stored in this capacitance. (5) is NW]l0LL where a COD transfer channel is formed, and (6) is a transfer gate. Here, a so-called buried channel is used as the transfer channel, but of course a surface channel may also be used. (γ) is a transfer gate that transfers signal charges to the transfer channel. Such conventional COD type image pickup devices have the following problems. This will be explained below.

Signal charges generated by incident light are stored in the capacitor (4). The amount of saturated charge is given by the following equation.

Q (saturated charge amount) = C (capacitance) It cannot be changed easily. Capacity is uniquely determined by the junction of (3) and (1),
(1) P type 5120~30Ω・(
If 1) is used, the capacitance is only about 2×10 4 PFAJ, and the problem is that the saturated amount of light is small because the amount of saturated charge is small.

〔the purpose〕

The present invention is intended to solve these problems, and its purpose is to provide a 00D-type image sensor with a large amount of saturated charge.

[Summary]

The OOD type image sensor of the present invention is characterized in that the junction capacitance is increased by forming a highly concentrated P type region under the N type diffusion layer that constitutes the light receiving diode.

[Examples] Hereinafter, the present invention will be described in detail based on Examples. FIG. 2 is a cross-sectional view of an embodiment of the invention. (8) is (
This is a P-type region with a higher concentration than the substrate concentration of (1), which is provided under the N-type diffusion layer of (3). The rest is the same as the conventional example shown in FIG. The junction capacitance of a photodiode with such a structure is, if the concentration of (8) is about 5 x 1016 cm-3, the capacitance value will be 7 x 10'P'F/crl, which is about 3 to 4 times that of the conventional example. The amount of saturation charge is improved.

Further, as the manufacturing method (8), it can be easily formed by using an ion implantation method or the like.

〔effect〕

As described above, according to the present invention, the junction capacitance of the photodiode is increased, and as a result, the saturated charge amount is increased, so that the saturated light amount is increased and the dynamic range is increased. In addition, the potency cooling distribution in the light-receiving area is as shown in Figure 5, and (8) also serves as a barrier for carriers generated in the deep region of the substrate, which can suppress smear phenomena caused by infrared light in particular. It also has the following advantages.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional OOD type solid-state imaging device, and FIG. 2 is a sectional view of an embodiment of the present invention. FIG. 3 shows the potential distribution of the light receiving portion of the present invention. (1)...P-type semiconductor substrate (2)...Insulating film (3)...N-type diffusion layer (4)...The junction capacity is ( 5)...NWFtLL region (6)...Transfer gate (7)...Transfer gate (8)...P-type region or above Applicant: Co., Ltd. Suiwa Seikosha

Claims (1)

[Claims] (1) A photodiode comprising a semiconductor substrate of a first conductivity type, at least two diffusion layers of a second conductivity type formed on the main surface of the semiconductor substrate, and a transfer gate for transferring the output of the photodiode. In a so-called CCD type solid-state imaging device consisting of a charge-coupled device that transfers the transferred output, a portion in contact with the photodiode,
A CCD type solid-state image sensor, characterized in that a region of a first conductivity type, which has a higher conductivity than the semiconductor substrate, is provided.