JPS63133666A - Solid-state image sensing device and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a solid-state image sensing device whose sensitivity in the region of short wavelengths from the visible spectrum, i.e., the so-call blue sensitivity, is improved by a method wherein a semiconductor layer where a lattice is matched to a crystal of a photodiode and a which can transmit the light better than a material for the photodiode is laminated on the photodiode. CONSTITUTION:A semiconductor layer 9 where a lattice is matched to a crystal of a photodiode and which can transmit the light better than a material for the photodiode is laminated on the photodiode. For example, a photoelectric transducer part of a CCD solid-state image sensing device is composed of a P-well 16, an n-type silicon layer 18 and a mixed crystal layer 9 of silicon and carbon (Si1-XCX); the constituent ratio of silicon to carbon inside the mixed crystal layer 9 is changed continuously from the ratio of carbon at 100% to the ratio of silicon to carbon at 50% to 50%. Through this constitution, the semiconductor layer 9 which can easily transmit the light does not generate a carrier even when it is illuminated by the light; is addition, the light in the region of short wavelengths from the visible spectrum can penetrate into a deep part; the carrier is generated where no interface with an oxide film exists; a device is difficult to be influenced by the interface level with the oxide film; the blue sensitivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a solid-state imaging device that can be used in video cameras, electronic still cameras, surveillance cameras, and the like.

BACKGROUND OF THE INVENTION In recent years, solid-state imaging devices have developed a structure in which a Pn junction photodiode is used for photoelectric conversion, the signal charge is stored in the photodiode, and the signal charge is transferred to a COD transfer channel using a MOS switch. Things are being mass produced.

Hereinafter, a conventional solid-state imaging device as described above will be explained with reference to the drawings. FIG. 3 is a sectional view of a conventional solid-state imaging device. A photodiode made up of an n-type semiconductor layer 1 and a p-type semiconductor layer 7 performs photoelectric conversion when irradiated with light to generate signal charges. The generated signal charges are accumulated on the surface of the n-type semiconductor layer 1. The accumulated signal charges are transferred to the n-type semiconductor layer 6 by applying a voltage to the gate 4 of the MOS switch. The n-type semiconductor layer 6 is a channel layer of a charge coupled device.

Problems to be Solved by the Invention However, in the above configuration, the depth of light penetration into silicon becomes shallow on the short wavelength side of the visible light range. Therefore, due to the influence of the interface state between the oxide film 3 and the n-type semiconductor layer 1, the sensitivity in the short wavelength side of the visible light range, so-called blue sensitivity,
The problem is that it's bad.

In view of the above drawbacks, the present invention provides a solid-state imaging device with improved blue sensitivity.

Means for Solving the Problems In order to solve the above problems, the solid-state imaging device of the present invention is made of a semiconductor that allows light to penetrate deeper than the semiconductor that forms the photodiode above the photodiode. layers are formed. In addition, the formation of the semiconductor layer with a deep penetration depth of light is performed using molecular beam epitaxial growth (MBK), photoepitaxial growth, or vapor phase epitaxial growth method (organic metal vapor phase epitaxial growth method, etc.) that allows low-temperature epitaxial growth. .

Effect With the above structure, the semiconductor layer where light penetrates deep does not generate carriers even when it receives light, and even light with short wavelengths in the visible light range can penetrate deeply, so that the interface with the oxide film is Since carriers are generated in areas where they are not present, they are less susceptible to the influence of interface states with the oxide film, and blue sensitivity is improved. Furthermore, by using a low-temperature epitaxial growth method, it is possible to reduce the diffusion of previously implanted impurities.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of a CCD solid-state imaging device according to an embodiment of the present invention.

The charge transfer section includes a transfer gate electrode 13. Oxide film 12 and n
shaped silicon layer 14. It is composed of a CCD consisting of P-well 16. The photoelectric conversion section includes a P-well 181, an n-type silicon layer 18, and a silicon-carbon mixed crystal layer (SiC
)s +−X X . The composition ratio of silicon and carbon in the mixed crystal layer 9 is continuously changed from 10% silicon to 60% silicon and 50% carbon. N-type silicon layer 18°P well 16. n
A vertical overflow drain structure is constructed to discard excess electrons accumulated in a shaped silicon substrate. A light shielding aluminum film 2 covers the CCD to prevent light from entering the charge transfer channels of the CCD.

One method for manufacturing the above structure is shown in FIG.

In the middle of the manufacturing method of a normal CCD solid-state imaging device, the
As shown in the figure, an n-type silicon layer 19. Pn of P well 2o
The oxide film on the junction photodiode is etched, and then, as shown in the figure, a mixed crystal layer 22 whose composition ratio of silicon and carbon is successively changed using molecular beam epitaxial growth.
form.

The thickness of the mixed crystal layer 22 is from 1,000 angstroms to several thousand angstroms. Next, as shown in FIG. 0, a silicon oxide film 23 is formed thereon by low pressure CVD, and a light shielding aluminum 24 is formed.

In this embodiment, the silicon and carbon compositions of the mixed crystal layer 9 are sequentially changed, but it is not necessary to sequentially change the compositions if the layers can be stacked without generating dislocations at the interface with silicon.

Although the constituent elements of the mixed crystal layer 9 in this embodiment are silicon and carbon, any material may be used as long as it has good crystal lattice matching with the n-type silicon layer 18 and has good transparency in the visible short wavelength range. It doesn't have to be crystal.

Further, in the manufacturing method of this embodiment, the molecular beam epitaxial growth method was used as the epitaxial growth method for the mixed crystal layer 22, but any low-temperature epitaxial growth method may be used, for example,
A low pressure CYD method using substrate heating or a photoepitaxial method may be used.

In addition, in the present invention, a CC using a Pn junction photodiode
D 5 with good light transmittance on the photodiode of the solid-state imaging device
Although the i1- and Cx layers are formed, any CCD solid-state imaging device may be used, for example, an S layer is formed between the oxide film and silicon layer of a CCD solid-state imaging device using a MOS capacitor photodiode.
An i, -xOx layer may also be formed.

Further, in the present invention, a CCD solid-state imaging device is used, but any solid-state imaging device may be used, such as an MO3 type solid-state imaging device.

Effects of the Invention As described above, the present invention provides a mixed crystal layer with good light transmittance and good lattice matching on top of the photodiode, which reduces the effects of interface states with the oxide film, and improves performance in the visible light range. Sensitivity to short wavelength light is improved, and its practical effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a solid-state imaging device of the present invention, FIG. 2 is a manufacturing process diagram of the solid-state imaging device of the present invention, and FIG. 3 is a cross-sectional view of a conventional solid-state imaging device. 9... Semiconductor layer through which light easily passes, 11...
...Interlayer insulating film, 18...n-type semiconductor layer. Name of agent: Patent attorney Toshio Nakao and 1 other personq
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Claims (2)

[Claims] (1) A solid-state imaging device characterized in that a semiconductor layer is laminated on a photodiode, the semiconductor layer having lattice matching with the crystal of the photodiode and transmitting light more easily than the photodiode material. (2) A photoelectric conversion section is formed by laminating a lattice-matched semiconductor layer on top of the photodiode through selective epitaxial growth using molecular beam epitaxial growth, photoepitaxial growth, or vapor phase epitaxial growth. 1. A method for manufacturing a solid-state imaging device, comprising: forming a solid-state imaging device.