JPH0644618B2 - Semiconductor light receiving device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor light receiving device in which a plurality of light receiving elements are formed in an array, and a semiconductor in which cross talk between the light receiving elements is reduced to improve measurement accuracy. The present invention relates to a light receiving device.

[Technical Background of the Invention and its Problems] With recent advances in semiconductor technology, semiconductor light receiving devices in which a plurality of semiconductor light receiving elements such as photodiodes are arranged in a light receiving portion are becoming widespread, and their application fields are considerably wide.
It has been put to practical use in each field. An example of such a semiconductor light receiving device is shown in FIG.
This is described in detail in Japanese Patent Application No. Showa 59-136171, which will now be outlined based on FIG.

FIG. 2 is a sectional view of the semiconductor light receiving device. N ⁻ type epitaxial layer 3a formed on P ⁻ type semiconductor substrate 1
3b to 3b are P ⁺ type element isolation diffusion regions 5a reaching the semiconductor substrate 1 from the surfaces of the epitaxial layers 3a to 3b.
It is divided into multiple islands by 5c. Then, by the PN junction formed between each of the N ⁻ type epitaxial layers 3a to 3c and the P ⁻ type semiconductor substrate 1 and each of the P ⁺ type element isolation diffusion regions 5a to 5c, FIG. In the three photodiodes 7a, 7b, 7c,
Each of the epitaxial layers 3a to 3c is formed as a cathode region, each of the element isolation diffusion regions 5a to 5c as an anode region, and the semiconductor substrate 1 as a common anode region for each of the photodiodes 7a to 7c. There is. Further, each anode region is grounded, and each cathode region is applied with a positive voltage via each cathode electrode 9a-9c,
Each of the photodiodes 7a-7c is reverse biased.

In such a configuration, the photodiodes 7a to 7c
When the surface of the semiconductor chip on which is formed is irradiated with light,
The irradiated light is absorbed in the semiconductor to generate electron-hole pairs. The minority carrier electrons generated in the semiconductor substrate 1 and the minority carrier holes generated in the epitaxial layers 3a to 3c are reverse-biased by diffusion into PN.
The light receiving region of the light reaching the junction and being extracted as a photocurrent from the cathode electrodes 9a to 9c and applied to the semiconductor light receiving device is measured.

In the semiconductor light receiving device as described above, the P ⁺ type semiconductor substrate 1 is used for each of the photodiodes 7a to 7a.
It is an anode region common to c. Therefore, for example, when the photodiode 7b is irradiated with light and some of the electrons generated at the position indicated by point A of the semiconductor substrate 1 are:
Due to the lateral diffusion, the photodiode 7a or 7
There is a problem that cross talk occurs even reaching the PN junction forming c.

Therefore, the PN of the photodiode 7a or 7c
The electrons reaching the junction are collected as a photocurrent, and the photocurrent also flows through the photodiode that does not receive the irradiation light, making it difficult to accurately measure the light receiving region.

[Object of the Invention] The present invention has been made in view of the above, and an object of the present invention is to suppress minority carriers that laterally diffuse between photodiodes formed adjacently on a semiconductor substrate. And to provide a semiconductor light receiving device with improved measurement accuracy.

[Summary of the Invention] In order to achieve the above object, a second conductivity type region of an epitaxial growth layer formed on a first conductivity type semiconductor substrate is separated by diffusion of the first conductivity type. A semiconductor light receiving device which is divided into a plurality of regions by regions, and a plurality of light receiving elements using PN junctions formed respectively between the regions divided into the plurality of regions and the isolation region and the semiconductor substrate are arranged. In the device, the gist of the present invention is that a high-concentration region of the same conductivity type as the isolation region is formed in the semiconductor substrate below the isolation region so as to reach the isolation region.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a semiconductor light receiving device according to an embodiment of the present invention. This semiconductor light receiving device is similar to the semiconductor light receiving device shown in FIG.
c is a P ⁺ -type element isolation diffusion region 5 on the semiconductor substrate 1.
The N ⁻ type epitaxial layers 3a to 3c, which are divided so as to be surrounded by a to 5c and to which a positive voltage is applied, are used as the cathode region, and the semiconductor substrate 1 and the grounded P ⁺ type element isolation diffusion region 5a to 5c is formed so as to be adjacent to the anode region. Using the photodiodes 7a to 7c formed in this way, the semiconductor light receiving device shown in FIG. 1 was irradiated on the light receiving surfaces of the photodiodes 7a to 7c, similarly to the semiconductor light receiving device shown in FIG. Using the light as a photocurrent, each of the cathode electrodes 9a to 9c
By taking it out from the photodiode 7 of the irradiation light
The light receiving areas on the light receiving surfaces a to 7c are measured.

The semiconductor light-receiving device of this embodiment is characterized by N
Each of the P ⁺ type element isolation diffusion regions 5a to be the anode regions of the photodiodes 7a to 7c while dividing the ⁻ type epitaxial layers 3a to 3c.
This is because the buried regions 11a to 11c of the same conductivity type as the element isolation diffusion regions 5a to 5c, that is, the P ⁺ type buried regions 11a to 11c are formed by diffusion under the portion 5c. This P ⁺ type buried region 1
1a to 11c have a diffusion depth of 10 μm or more and a sheet resistance of 10 to 30 Ω / port.

Thus, in the semiconductor substrate 1 below the P ⁺ type element isolation diffusion regions 5a to 5c, the P ⁺ type buried regions 11a to 11 are formed.
The structure having c is formed by using a standard bipolar process in which a semiconductor light receiving device is formed. In such a structure, after the N ⁺ type buried diffusion is performed on the P ⁺ type semiconductor substrate 1 in the standard bipolar process,
It is formed only by adding a P ⁺ -type diffusion step.

Then, the P ⁺ type diffusion process is completed, and each P ^{+ type}
After the buried regions 11a to 11c of the type are formed in the semiconductor substrate 1, an N ⁻ type epitaxial layer is grown on the semiconductor substrate 1 in which the P ⁺ type buried regions 11a to 11c are formed to form P ^+. Form element isolation diffusion regions 5a-5c,
The element isolation diffusion regions 5a to 5c divide the N ⁻ type epitaxial layer. Next, N ⁻ type emitter diffusion regions 13a to 13c for connecting the cathode electrodes 9a to 9c to the divided epitaxial layers 3a to 3c, respectively.
Forming a contact hole, cathode electrode 9
Aluminum wirings for a to 9c are formed, and the semiconductor light receiving device shown in FIG. 1 is completed.

In the semiconductor light receiving device having the above-described structure, the photodiode 7b is irradiated with light, and the absorption of the irradiated light causes the electron-hole pair to be at the same position as point A shown in FIG. When the electrons are generated at the point B shown in (1), some of the pair-generated electrons move laterally due to diffusion. The electrons that have moved in the lateral direction reach the P ⁺ type buried regions 11b and 11c, and most of the electrons are accumulated in the buried regions 11b and 11c and recombined with holes. Therefore, the photodiodes 7a and 7c are
No photocurrent is generated by the electrons generated at the point. Therefore, the cross talk between the photodiodes 7a to 7c is significantly reduced, and the respective photodiodes 7a to 7c generate a photocurrent by the light applied to their light receiving surfaces to accurately receive the light. The area is measured. In addition, in particular, for detecting long wavelength light, P
Although it is necessary to make the N junction surface as deep as possible, according to the device configuration of this embodiment, since the diffusion regions 5a to 5c are formed after the buried regions 11a to 11c are formed, the position of the PN junction surface is formed. Even if the depth is deep, it is possible to accurately detect long-wavelength light while suppressing an increase in the area of the diffusion region as compared with the conventional case.

As described above, according to the present invention, since the high-concentration region of the same conductivity type as the isolation region is formed in the semiconductor substrate below the isolation region formed by diffusion, It is possible to suppress the lateral diffusion of the electrons generated in the semiconductor substrate by the absorption of, and to significantly reduce the cross talk between the light receiving elements. As a result, it is possible to provide a semiconductor light receiving device that measures the light receiving region with high accuracy.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor light receiving device according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional semiconductor light receiving device. (Explanation of Reference Signs Representing Main Portion of Drawing) 1 ... Semiconductor substrate 3a to 3c ... N ^-- type epitaxial layer 5a to 5c ... P ⁺ type element isolation diffusion region 7a to 7c ... Photodiode 11a to 11c ... ... P ⁺ type embedded area

Claims (1)

[Claims] 1. A second conductivity type region of an epitaxial growth layer formed on a first conductivity type semiconductor substrate is divided into a plurality of regions by an isolation region formed by diffusion of the first conductivity type. A plurality of light receiving elements each using a PN junction formed between the region divided into the plurality of regions and the isolation region and the semiconductor substrate, and In the semiconductor substrate, a high-concentration region of the same conductivity type as the isolation region is formed so as to be in contact with the isolation region.