JPS5812744B2 - semiconductor equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device including a photoelectric conversion element manufactured through an IC process.

As semiconductor devices are used in a variety of electronic devices, in addition to conventionally known IC circuit elements such as diodes and transistors, phototransistors or photodiodes that output electrical signals in response to light have been integrated into the same semiconductor chip. Semiconductor devices have been put into practical use, and have a function of responding to optical signals.

This type of semiconductor device is manufactured using conventionally known IC manufacturing technology, and as shown in FIG. N0 buried layers 2, 2' in the area corresponding to
is formed in advance, an N-type epitaxial layer 3 is grown thereon, and impurities are diffused into the epitaxial layer 3 on the embeddings 12 and 2' in a desired pattern to form IC circuit elements Tr such as transistors and diodes. At the same time, a photoelectric conversion element PD such as a photodiode is manufactured within the same chip.

In the semiconductor device having the above structure, the photoelectric conversion element region PD
When irradiated with light, the light energy generates pairs of electrons and holes in the silicon semiconductor, and these move to the N region and P region within the photoelectric conversion element, resulting in output (Fig. (●: electron, ○: hole).

However, in the above-mentioned semiconductor device in the operating state, the space between the epitaxial growth layer (collector) and the substrate is normally reverse biased, and among the electron-hole pairs generated by the optical energy absorbed by the epitaxial layer, the substrate A pair generated in a portion close to 1 results in a flow between the collector and the substrate, and cannot be derived as a photoelectric conversion element output, resulting in the inconvenience that the function of the device cannot be achieved.

In particular, a light-emitting element such as GaAs as a light source that has an emission intensity on the relatively long wavelength side has the disadvantage that the light-receiving sensitivity is significantly reduced.

In other words, the longer wavelength light has the characteristic that it penetrates deeper into the semiconductor surface and is absorbed, and electron-hole pairs are generated near the reverse biased PN junction, and cannot be extracted as output due to the influence of the reverse bias. It turns out.

A possible solution to the above problem is to make the epitaxial growth layer thicker, but if the epitaxial growth layer is made thicker, the insulation isolation function between IC circuit elements incorporated in the same chip becomes more efficient. There are unresolved problems, and the maximum thickness of the epitaxial layer is about 15 μm.

It is also possible to compensate for the decrease in light-receiving sensitivity by increasing the light-receiving area, but this is not preferred as it would lead to an increase in the size of the device.

The present invention has been made in view of the above-mentioned problems with the conventional device, and it is an object of the present invention to provide a semiconductor device that can improve the long wavelength sensitivity characteristics of a photoelectric conversion element by simply adding a simple configuration.

The present invention will be explained in detail below using the drawings.

In FIG. 2, reference numeral 10 denotes a silicon semiconductor substrate exhibiting P-type conductivity, and the main surface of the substrate 10 is highly doped with N-type impurities in regions corresponding to IC circuit elements and photoelectric conversion elements by a process described later. N-type buried layers 11 and 12 are provided which are diffused in concentration.

Here, while the buried layer 11 corresponding to IC circuit elements such as diodes and transistors is provided at a depth (several microns to several microns) similar to that of conventional devices, photodiodes,
Buried layer 1 corresponding to photoelectric conversion elements such as phototransistors
No. 2 is provided with a deep diffusion depth of several tens of microns (approximately 50 microns).

That is, in the photoelectric conversion element portion, the bottom surface of the pN junction between the buried layer 12 and the substrate 10 is located further away from the main surface.

In the production of each of the buried layers 11 and 12, impurities are first diffused into the region corresponding to the buried layer 12 to penetrate sufficiently deeply, and then the buried layer 12 is masked to form a region corresponding to the buried layer 11. This is obtained by shallowly diffusing impurities into the region where the

Furthermore, in order to improve the lifetime of minority carriers by increasing the lifetime of electron-hole pairs generated by light energy, the buried layer 12 is made with impurities that lower the surface concentration (for example, phosphorus with a large diffusion coefficient). ) and diffusion treatment conditions are preferably selected.

An N-type epitaxial growth layer 13 is formed on the substrate 10 in which both of the N-type buried layers 11 and 12 are diffused, and electrical connection is established between each IC circuit element and photoelectric conversion element planned for the epitaxial growth layer 13. P-sufficiently separated regions 14, 14, . . . for separation are provided.

P and N impurities are diffused into the N-type island region 15 surrounded by the P+ isolation region 14 to form a diode and a transistor, and at the same time, desired A photoelectric conversion element such as a photodiode or a phototransistor is formed by diffusing P and N impurities into a shape that provides light-receiving sensitivity characteristics.

In the semiconductor device having the above structure, since the buried layer in the region where the photoelectric conversion element is installed is formed deeper in advance, even if an electron-hole pair generated by long wavelength light energy is generated between the collector substrate The degree of absorption by the PN junction is significantly reduced compared to conventional devices, and therefore the irradiated light can be effectively photoelectrically converted, and the operating characteristics of the device can be improved.

Furthermore, since the photoelectric conversion efficiency is improved, the area of the light-receiving region of the photoelectric conversion element can be reduced even when obtaining the same output as a conventional device, and the device can be made smaller and less expensive.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a conventional device, and FIG. 2 is a sectional view of a main part of an embodiment according to the present invention. 10... Semiconductor substrate, 11, 12...
N-type buried layer, 13...Ebitaxial growth layer,
14...Insulating isolation region, 15...IC
Circuit element, 15'...Photoelectric conversion element.

Claims (1)

[Claims] 1. In a semiconductor device in which an IC circuit element such as a diode or a transistor and a photoelectric conversion element are provided on each buried layer in the same chip, the depth of the buried layer in which the photoelectric conversion element is provided is determined by the depth of the IC circuit element. 1. A semiconductor device characterized in that the semiconductor device is formed sufficiently deeper than a buried layer in which a buried layer is provided.