CN1023853C - Ultraviolet enhanced inversion layer type photodiode - Google Patents

Abstract

An improved ultraviolet-enhanced inversion layer type photodiode is prepared by combining an inversion layer structure with N⁺The diffusion ring combines the structures that the leakage current outside the working area is led away and does not enter a current loop of the working area, so that the ultraviolet enhancement effect is good, the leakage current is small, the breakdown voltage is high, the performance is stable, the manufacturing process is simple and convenient, and the yield is high.

Description

Manufacturing method of ultraviolet enhancement photodiode

The invention belongs to the structure of optical semiconductor sensing device.

For surveying ultraviolet light, existing polytype silicon photo-detector is as Schottky barrier type, shallow diffused junction type, transoid stratotype, N ⁺-N-P type, shallow arsenic diffusion type or the like.Transoid stratotype device is to make like this: heat growth layer of silicon dioxide film on P type silicon chip, utilize in silicon dioxide-system on silicon, the induction effect that has fixed positive charge in the thin layer scope near the surface in the silicon dioxide layer, inducing the negative electrical charge of equivalent at P type silicon face, only is the inversion layer of tens dusts to the hundreds of dust and form thickness.On the regional area of this inversion layer (being N type district), make strip or point-like N again with the method that expands N type impurity ⁺The district is as the extraction electrode of inversion layer (being N type district).And make ohmic contact in the p type island region territory, as the extraction electrode of p type island region.Thereby make a photodiode.But because the zone beyond the service area also can form inversion layer, and extends to the silicon chip border always, breakdown potential is forced down so above-mentioned device has, reverse leakage current is big, shortcomings such as poor reliability.

In order to overcome this shortcoming, before the present invention, people adopted following two class ways.One class way is, beyond the service area, the diffusion of high concentration p type impurity is implemented on the surface of P type substrate, though making has positive charge to exist, and can not induce inversion layer in addition in the service area, another kind of way is, beyond the service area, remove and contain the many silicon dioxide layers of positive charge, make one deck again and contain positive charge silicon dioxide layer seldom, thereby make and not generate inversion layer beyond can be in the service area.Practice shows, implements above-mentioned way, and technology is more tired, and effect repeatability is relatively poor, and performance is not quite stable.

Purpose of the present invention is that the structure to transoid stratotype silicon photo-detector makes improvements, and specifically, is also to have inversion layer beyond allowing the service area, but makes the existence of this inversion layer, does not influence the work of service area.

Task of the present invention is finished in the following manner: on the limit, service area, form an annular strip N around the sealing of service area by diffusion N type impurity ⁺ ₁The district, as the extraction electrode of service area, the zone that this ring is enclosed is the service area, at N ⁺ ₁Beyond the ring, form one by diffusion N type impurity again and surround N ⁺ ₁The ring, but not with N ⁺ ₁The annular strip N of the sealing that ring is connected ⁺ ₂The district.During use, P type substrate connects power cathode, N ⁺ ₁Receive positive source, N again by load resistance ⁺ ₂The district then directly links to each other with positive source.Under this operating position, N ⁺ ₁District and N ⁺ ₂Zone between the district will present high impedance, service area and N ⁺ ₂Nonclient area beyond the district is kept apart, and the leakage current of nonclient area can not enter the service area current circuit.Thereby, both made the service area that extremely shallow induced junction is arranged, little leakage current and high stability are arranged again.And it is simple for production.

Accompanying drawing 1 is the front view of tube core structure.

Accompanying drawing 2 is profiles of tube core structure.

Embodiment.Adopting resistivity is that the above P type silicon single crystal of 1 ohmcm is as substrate.Routinely planar technique polish, thermal growth oxide layer, about 4000 dusts of thickness make the N as accompanying drawing 1 by lithography ⁺ ₁And N ₂And N ⁺ ₂The district carves fairlead, evaporation of aluminum, photoetching, formation N then ⁺ ₁District, N ⁺ ₂District and P district bottom surface ohmic contact have just been finished die making.Again with the tube core sintering on base, and respectively from N ⁺ ₁District, N ⁺ ₂Totally three lead-out wires are drawn in district and bottom surface P district, put on the pipe cap of the good optical transmission window of ultraviolet light performance at last.

Claims (1)

1, a kind of ultraviolet strengthens transoid stratotype photodiode, heat growth layer of silicon dioxide film on P type silicon chip, with the silicon chip of this film with one side on annular strip N is set ⁺ ₁The district is characterized in that, an encirclement N is being set ⁺ ₁Ring, but not in N ⁺ ₁The closed ring strip N that ring connects ⁺ ₂The district.

Images