JPH04280678A - Solid-state image pickly element - Google Patents

Abstract

PURPOSE:To dispense with color filters by a method wherein a substrate is formed of GaAs or the like, and a photodiode array is composed of photodiodes formed of three kinds of semiconductors of GaAs/AlGaInP. CONSTITUTION:A photodiode PRGB is formed of GaAs and photoelectrically converts light 0.87mum or below in wavelength or red, gree, and blue light. A photodiode PGB which photoelectrically converts light 0.58mum or below in wavelength or green and blue light is formed of (Al0.4Ga0.6)0.51In0.49P. A photodiode PB which photoelectrically convertsw light 0.53mum or below in wavelength or blue light is formed of (Al0.7Ga0.3)0.51In0.49P. Signals obtained through the photodiodes arranged in this manner are processed by an external image processing device to obtain luminance signals, color signals, and color difference signals as required.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a solid-state image sensor,
In particular, the present invention relates to a solid-state image sensor that enables color filtering without using a color filter.

0002

2. Description of the Related Art A conventional solid-state image sensor is formed using Si, and as shown in FIG. A vertical register (vertical CCD) 3 for transferring, a charge reading section 2 for reading signal charges accumulated in the photodiode 1 to the vertical register 3, and a horizontal register (horizontal CCD) 4 for transferring signal charges in the horizontal direction. , and an amplifying section 5 that converts the signal charge into a voltage signal and amplifies this voltage signal.

The fundamental absorption edge wavelength λ0 of a solid-state image sensor is given by the forbidden band width Eg of the semiconductor, as λ0≈hc/Eg (h: Planck's constant, c: speed of light). h, c
Substituting the value of λ0 [μm] = 1.2398/Eg [eV],
In Si, Eg = 1.11 eV, so λ0 = 1.
It becomes 12 μm.

[0004] Therefore, in conventional solid-state image sensors using Si, photoelectric conversion is performed on light of wavelengths shorter than near-infrared rays.

[0005] Conventional photodiodes did not have the function of distinguishing colors, so in order to obtain a video signal including color signals, red, green, and
It was necessary to provide a color filter in which dyed layers such as blue are regularly arranged.

[0006]

[Problems to be Solved by the Invention] In the conventional solid-state imaging device described above, it was necessary to provide a color filter to enable color imaging, but the color filter required at least three dyed layers. Therefore, in order to create this, it was necessary to repeat the patterning of the dyed layer, the dyeing, the formation of the protective layer, etc. for each layer, which required a large amount of man-hours. Furthermore, accurate alignment between each color filter layer and the photodiode was required for each layer.

Furthermore, since color filters are formed using organic materials, they have problems with heat resistance and moisture resistance, and have the disadvantage that they are easily deteriorated by heat treatment during the assembly process, for example.

Furthermore, since the conventional example performs photoelectric conversion on near-infrared light of 0.9 to 1.1 μm, the solid-state imaging device using the conventional example must be provided with an infrared cut filter, which is an inconvenience. was there.

[0009]

[Means for Solving the Problems] The solid-state imaging device of the present invention uses GaAs or the like as a substrate, and the photodiode is
It is made of aAs/AlGaInP material. That is, the photodiode is made of, for example, ■GaAs, ■(A
l0.4 Ga0.6 )0.51In0.49P,■
(Al0.7 Ga0.3 )0.51In0.49P
It is composed of three types of semiconductors.

0010

[Operation] Since the forbidden band width of GaAs is Eg = 1.43 eV, the fundamental absorption edge wavelength is λ0 = 0.87 μm, and photoelectric conversion is performed for light of all wavelengths in the visible light region, and Almost no photoelectric conversion is performed on infrared rays.

(Al0.4 Ga0.6 )0.51I
The n0.49P mixed crystal semiconductor is well lattice matched to GaAs, and its forbidden band width is Eg = 2.15 eV, so
The fundamental absorption edge wavelength is λ0 = 0.58 μm, and photoelectric conversion is performed for visible light with wavelengths in the green and blue regions.

[0012] Also, (Al0.7 Ga0.3)0.
The mixed crystal semiconductor of 51In0.49P is well lattice-matched to GaAs, and its forbidden band width is Eg = 2.33 eV, so the wavelength of the fundamental absorption edge is λ0 = 0.53 μm, which is visible light in the blue region. Photoelectric conversion will be performed on the

By configuring a photodiode array using the three types of semiconductors mentioned above, without using color filters, it is possible to: (1) photoelectrically convert the red, green, and blue regions, and (2) convert only the light in the green and blue regions. It is possible to obtain a solid-state image sensor having three types of regions: a portion that photoelectrically converts light, and (1) a portion that photoelectrically converts only light in the blue region.

[0014]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic plan view showing an embodiment of the present invention, and FIG. 2 is a plan view showing an arrangement of photodiodes thereof.

As shown in FIG. 1, the solid-state imaging device of this embodiment includes a photodiode 1 that performs photoelectric conversion and accumulates signal charges, and a vertical register (vertical CCD) 3 that transfers signal charges in the vertical direction. , a charge readout section 2 for reading out the signal charge accumulated in the photodiode 1 to the vertical register 3, a horizontal register (horizontal CCD) 4 for transferring the signal charge in the horizontal direction, and converting the signal charge into a voltage signal. In this respect, there is no difference from the conventional example shown in FIG. 4. However, this embodiment is mainly composed of GaAs, and the photodiode is made of GaAs/AlGaIn.
It is formed using a P-based material.

In FIG. 2, the photodiode designated PRGB is made of GaAs and has a diameter of 0.87
Photoelectric conversion is performed on light with a wavelength of μm or less, that is, light in the red, green, and blue regions.

A photodiode that performs photoelectric conversion on light in the green and blue regions with a wavelength of 0.58 μm or shorter is made of (Al0
．． 4Ga0.6)0.51In0.49P, and is labeled PGB.

In addition, a photodiode that performs photoelectric conversion on light in the blue region with a wavelength of 0.53 μm or shorter is made of (Al
It is composed of 0.7Ga0.3)0.51In0.49P and is designated as PB.

Signals obtained from the photodiodes arrayed as shown in FIG. 2 are processed by an external image processing device to obtain desired luminance signals, color signals, and color difference signals.

Next, a method of manufacturing the embodiment shown in FIGS. 1 and 2 will be briefly described. n on a p-type GaAs substrate
A type GaAs layer is grown using a liquid phase method, and Si is deposited on top of it.
Deposit the O2 layer. After selectively etching away the SiO2 layer and the n-type GaAs layer at the location where the photodiode indicated as PGB is to be formed, an n-type (Al0.4 Ga0.6 )
0.51In0.49P was grown, followed by SiO2
By etching away the layer, the n-type (Al0.
4. A substrate having a structure in which Ga0.6)0.51In0.49P is embedded is created. Using a similar method, n-type (Al0.7 Ga0.3)0.
51In0.49P is embedded.

Next, Zn is applied to the region that will become the charge readout section 2.
This region is made p-type by ion implantation, and then protons are ion-implanted into the region excluding the photodiode 1, the charge readout section 2, the vertical and horizontal register sections 3 and 4, and the amplification section 5, except for the active region. Insulate the area. Next, a transfer electrode and a light shielding film are formed.

FIG. 3 is a plan view showing a photodiode array according to another embodiment of the present invention. PRG as in Figure 2
B, PGB, and PB are light in red, green, and blue regions with wavelengths shorter than 0.87 μm, light in green and blue regions with wavelengths shorter than 0.58 μm, and blue light with wavelengths shorter than 0.53 μm, respectively. These photodiodes are shown to perform photoelectric conversion on the image, and these photodiodes are formed using the same materials as in the previous embodiment.

In the above embodiment, the photodiodes other than the GaAs photodiode are of a heterojunction type, but this may be changed so that all of the photodiodes are of a homojunction type. Furthermore, Si as a substrate
may be used, and only the photodiode may be made of a compound semiconductor. Further, the present invention can be applied not only to area-type solid-state image sensors but also to linear-type solid-state image sensors, and not only to CCD solid-state image sensors but also to other types of solid-state image sensors such as CID solid-state image sensors.

[0024]

As explained above, in the solid-state imaging device according to the present invention, photodiodes made of various compound semiconductors having different fundamental absorption edge wavelengths are arranged in an array or matrix, and the photodiodes themselves have color Since it is configured to have a filtering function, the present invention eliminates the need to create a color filter layer, and eliminates the need for complicated processes and processes that require accurate alignment. Furthermore, since it is no longer necessary to use organic materials, it becomes possible to provide a solid-state imaging device with excellent heat resistance and moisture resistance.

Furthermore, according to the present invention, since a photodiode that is hardly sensitive to infrared rays is used, there is no need to use an infrared cut filter.

Furthermore, when GaAs is used as the substrate, the lattice constants of the substrate and photodiode are well matched, so that the generation of dark current can be minimized.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of an embodiment of the present invention.

FIG. 2 is a diagram showing the arrangement of photodiodes in the embodiment of FIG. 1;

FIG. 3 is a diagram showing the arrangement of photodiodes in another embodiment of the present invention.

FIG. 4 is a schematic plan view of a conventional example.

[Explanation of symbols]

1 Photodiode 2 Charge readout section 3 Vertical register 4 Horizontal register 5 Amplification section

Claims (1)

[Claims] 1. A solid-state imaging device in which a plurality of photodiodes each made of one of a plurality of material groups having different basic absorption edges are arranged in an array or a matrix, wherein the plurality of material groups have different fundamental absorption edges. is GaAs
A solid-state imaging device characterized in that it is selected from materials of the /(AlxGa1-x)yIn1-yP (where 0<x, y<1) system.