JPH036056A - Photodiode - Google Patents

Abstract

PURPOSE:To obtain a high spectral-sensitivity characteristic over a wide wave length range by a method wherein a P-type base diffusion layer and an N-type emitter diffusion layer are formed one after another in a position which faces a floating collector layer and a P-type rear-surface isolation layer and on the surface of the photodetection side of an N-type epitaxial layer. CONSTITUTION:The following are formed: a first photodiode part which is composed of an N-type emitter diffusion layer 30 and of a P-type base diffusion layer 20; a second photodiode part which is composed of the P-type base diffusion layer 20 and of an N-type epitaxial layer 4; and a third photodiode part which is composed of the N-type epitaxial layer 4 and of a P-type rear-surface isolation layer 9. In addition, the following are formed respectively: a fourth photodiode part which is composed of a P-type rear-surface isolation layer 90 and of a floating collector layer 100; and a fifth photodiode part which is composed of the floating collector layer 100 and of a P-type substrate 5. P-N junction faces of the individual photodiode parts exist respectively in positions whose depth from the surface is physically different. Thereby, it is possible to obtain a high spectral-sensitivity characteristic over a wide wavelength range.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a photodiode with improved spectral sensitivity characteristics.

<Prior Art> FIG. 3 is a sectional view showing the structure of a conventional photodiode. In the figure, 1 is a P-type separation diffusion layer, 2 is a P-type isolation diffusion layer, and 2 is a P-type separation diffusion layer.
3 is an N-type emitter diffusion layer, 4 is an N-type epitaxial layer, 5 is a P-type substrate, 6 is a cathode electrode, 7
is the anode electrode. In this configuration, when irradiated with light, the PN between the N-type epitaxial layer 4 and the P-type substrate 5 is
Carriers are generated near the bonding surface, and as shown in FIG. 4, when the cathode 6 and anode 7 are connected, a current flows between them.

<Problem to be solved by the invention> By the way, in general, the shallower the depth from the light-receiving surface to the PN junction surface, the better the spectral sensitivity on the short wavelength side;
The deeper the depth from the light-receiving surface to the PN junction surface, the better the spectral sensitivity on the long wavelength side tends to be. However, in the conventional method, one P is placed at a certain depth from the light receiving surface.
Since there is only an N-junction surface, the dependence on the wavelength of light is noticeable. That is, as shown by the dashed line in FIG. 5, the conventional photodiode has a narrow wavelength region with high spectral sensitivity, which limits the wavelength range in which the photodiode can be used satisfactorily.

<Means for Solving the Problems> The present invention has been made in view of the above circumstances, and is intended to make it possible to obtain a wavelength region with high spectral sensitivity over a wide range.

Therefore, the present invention employs the following configuration in a photodiode in which an N-type epitaxial layer is formed on a P-type substrate.

That is, in the photodiode of the present invention, while a floating collector layer and a P-type bottom isolation layer are sequentially formed on the surface of the P-type substrate on the N-type epitaxial layer side, the floating collector layer and the P-type bottom isolation layer are A P-type base diffusion layer and an N-type emitter diffusion layer are sequentially formed at opposing positions and on the light-receiving side surface of the Moeki N-type epitaxial layer.

<Function> According to the above configuration, the first photodiode section is made up of an N-type emitter diffusion layer and a P-type base diffusion layer, the second photodiode section is made up of a P-type base diffusion layer and an N-type epitaxial layer, and the N-type epitaxial layer. a third photodiode section consisting of a P-type lower surface portion MPJ and a floating collector layer; and a fifth photodiode section consisting of a floating collector layer and a P-type substrate.
A total of five types of photodiode sections are respectively formed. Since the PN junction surface of each photodiode section is located at five locations at physically different depths from the surface, high spectral sensitivity characteristics can be obtained over a wide wavelength range from the short wavelength side to the long wavelength side. You will be able to do it. Furthermore, since carriers are generated in the vicinity of each PN junction surface, the absolute value of sensitivity is improved overall.

<Embodiment> Fig. 1 is a cross-sectional view showing the configuration of a photodiode according to an embodiment of the present invention, and Fig. 2 is an equivalent circuit diagram of the photodiode shown in Fig. 1. , are given the same symbols.

In these figures, 2 is a P-type base diffusion layer, 3 is an N-type emitter diffusion layer, 4 is an N-type epitaxial layer, 5 is a P-type substrate, 6 is a cathode electrode, 7 is an anode electrode, and 8 is a P-type bottom isolation layer. Layer 9 is a P-type bottom separation layer.

The feature of this embodiment is that a floating collector layer 10o and a P
A P-type bottom isolation layer 9° is sequentially formed, while a P-type epitaxial layer 4 is formed on the light-receiving side surface of the N-type epitaxial layer 4 at a position opposite to the floating collector layer 10° and the P-type bottom isolation layer 9°. Base diffusion R2...! : An N-type emitter diffusion layer 3° is formed in sequence. Each P type base diffusion layer 2.2o has an anode electrode 7.1.
3.14 are respectively provided, and these anode electrodes 7.13.14 are connected with aluminum wiring or the like to constitute an anode terminal 20. In addition, the N-type emitter diffusion layer 3
．． 3o is provided with cathode electrodes 6 and I3, respectively,
Each of these cathode electrodes 6.13 is connected with aluminum wiring or the like to constitute a cathode terminal 21.

Therefore, in the photodiode having the above configuration, the first photodiode section DI consists of the N-type emitter diffusion W13° and the P-type base diffusion layer 2°, the P-type base diffusion layer 2° and the N-type base diffusion layer 2°.
A second photodiode section D2 consisting of a type epitaxial layer 4, a third photodiode section D3 consisting of an N type epitaxial layer 4 and a P type lower surface M layer 9°, a P type lower surface separation layer 9.
A fourth photodiode section D4 consisting of a floating collector layer 100 and a fifth photodiode section D consisting of a floating collector layer lOo and a P-type substrate 5.
A total of five types of photodiode portions (5) are formed locally. And each photodiode section DI-D5
Since the PN junction surfaces are located at five different depths from the light-receiving surface, carriers are generated near each PN junction surface depending on the wavelength of the incident light.

Therefore, as shown by the solid line in FIG. 5, high spectral sensitivity characteristics can be obtained over a wide wavelength range from the short wavelength side to the long wavelength side. Furthermore, since carriers are generated in the vicinity of each PN junction surface, the absolute value of sensitivity is improved overall.

<Effects of the Invention> According to the present invention, since the PN junction surface is formed at five positions physically different in depth from the light-receiving surface, high Spectral sensitivity characteristics can now be obtained. Furthermore, since carriers are generated in the vicinity of each PN junction surface, excellent effects such as an overall improvement in the absolute value of sensitivity are exhibited.

[Brief explanation of the drawing]

1 and 2 relate to embodiments of the present invention, with FIG. 1 being a sectional view showing the structure of a photodiode, and FIG. 2 being an equivalent circuit diagram of the photodiode shown in FIG. 3 and 4 relate to a conventional example, with FIG. 3 being a sectional view showing the structure of a photodiode, and FIG. 4 being an equivalent circuit diagram of the photodiode shown in FIG. FIG. 5 is a characteristic diagram showing a comparison of the spectral sensitivities of a photodiode according to an embodiment of the present invention and a conventional example. 2゜...P type base diffusion layer, 3o...N type emitter diffusion layer, 4...N type epitaxial layer, 5...P type substrate, 9.9o...P type bottom separation layer, lOo...Floating collector layer.

Claims (1)

[Claims] (1) In a photodiode in which an N-type epitaxial layer is formed on a P-type substrate, a floating collector layer and a P-type bottom isolation layer are sequentially formed on the surface of the P-type substrate on the N-type epitaxial layer side. , a P-type base diffusion layer and an N-type emitter diffusion layer are sequentially formed on the light-receiving side surface of the N-type epitaxial layer at positions facing the floating collector layer and the P-type bottom separation layer. photodiode.