JPS6281780A - Manufacture of light receiving element - Google Patents

Abstract

PURPOSE:To obtain a light receiving element, whose breakdown voltage is high, by implanting ions of a P-type dopand and III-group atoms, in order to form a P-type guard ring. CONSTITUTION:With an SiO2 film or an Si3N4 film as masks, Cd is diffused in a light receiving region and a P<+> InP layer 5 is formed. By the diffusion of Cd, very steep, staircase-shaped junction can be obtained at the front of diffusion. Then, with an SiO2 film 7, in which a guard ring region is opened, as a mask, Be ions are implanted, so that the implanting energy is 150keV an the amount of dose is 5X10<13>cm<-2>. Then Al ions are implanted so that the implanting energy is 500keV and the amount of dose is 5X10<14>cm<-2>. By the activating annealing of the ion implanted part, the inclination of impurity concentration is gentle and a deep guard ring 6 can be formed. Thus the formation of the light receiving element part is finished. The SiO2 film 7 is removed, and an Si3N4 film 8 for forming an electrodes is newly laminated. A P-type electrode 9 is formed with Au/Zn/Au, and an N-type electrode is formed with AuGe.

Description

[Detailed Description of the Invention] [Summary] As a semiconductor photodetector, avalanche photodiodes (APDs) have features such as low dark current, low noise, and high amplification, and are widely used for optical communications. In order to exhibit this feature in the structure, it is necessary to form a guard ring surrounding the light-receiving surface and make the breakdown voltage in this region higher than that of the light-receiving surface.The present invention improves the manufacturing method to achieve this. This made it easy to implement.

[Industrial application field]

The present invention relates to a semiconductor photodetector (AP) used for optical communication.
D) Regarding improvement of the manufacturing method.

A light-receiving element structure that can separate a light absorption layer and a multiplication layer, that is, S
AM type (Separated Absorption)
and Multtplication Regi
ons) APD is known to be suitable for optical communication as a light receiving element having low dark current and high amplification characteristics.

In this SAM type structure, a pn junction with p-type impurities introduced is formed in contact with the n-type multiplication layer in the light-receiving surface region.
In order to obtain low dark current and high amplification characteristics, it is necessary to provide a guard ring around this pn junction and to make the breakdown voltage of the guard ring portion higher than that of the light-receiving surface region.

As a means for achieving this, various improvements have been proposed in the structure and manufacturing method of the guard ring region, but further improvements are desired.

[Conventional technology]

APDs using InP are widely used for optical communications in the wavelength band of 1.3 to 1.6 μm.

A conventional InP APD structure will be explained with reference to the cross-sectional view of FIG. Since the present invention mainly relates to the structure of the guard ring portion, parts of the structure other than the guard ring that are not related to the present invention will be omitted from description.

In FIG. 2(a), 1 is an n''-InP substrate, 2 is an r
l-1nGaAsP light absorption layer, 3 is n-InP multiplication layer,
4 indicates an n--InP layer.

The above structure can be obtained by sequentially stacking layers starting from the substrate using a liquid phase growth method. Next, a p''-InP layer 5 is formed by diffusing Cd using a mask that opens the light-receiving surface.

Furthermore, using a mask that opens only the guard ring region, Be ions are implanted into the above structure to form a p-type guard ring 6. This state is shown in FIG. 2 (bl).

A stepped pn junction is formed at the junction surface between the p''-InP layer 5 and the n-InP multiplication layer 3 in the light receiving section, and a sloped pn junction is formed at the guard ring section.

This is because by forming a pn junction by introducing impurities separately as described above, the electric field strength of the guard ring portion is lower than that of the light receiving portion, and as a result, the breakdown voltage of the guard ring portion is increased.

Although a quaternary compound of InGaAsP is used as the light absorption layer in FIG. 2, a ternary compound of InGaAs may also be used, and a two-layer structure of a ternary layer and a quaternary layer is also used.

[Problem that the invention seeks to solve]

In the conventional method of forming a guard ring by implanting Be ions as described above, a sufficient reduction in electric field strength cannot be obtained, and the breakdown voltage is often still insufficient.

To solve this problem, the APD structure has a p”
-In There are many cases in which the problem has been solved by improving the shape and manufacturing method of the peripheral parts of the P layer 5 and the guard ring 6, but all of these methods require complicated processes and may lead to a decrease in cost and yield. There are many.

The present invention aims to improve the breakdown voltage using an extremely simple method without complicating the manufacturing process.

[Means for solving problems]

The above problem is that in APDs using m-v group compound semiconductors, when forming a guard ring surrounding the light-receiving surface by ion implantation, in addition to the p-type or n-type dopants that are required, This problem is solved by the manufacturing method of the present invention, which comprises further ion implantation of group V or group V atoms.

That is, in order to form p-type guards and dolings, p-type dopants and group II atoms are ion-implanted, respectively.

In addition, in the case of an n-type guard ring, the n-type dopant and ■
The problem is solved by applying a method of ion-implanting each of the group atoms.

[Effect]

When forming a p-type impurity region in the n-layer of an m-v group compound semiconductor using an ion implantation method, it is necessary to further inject AI of group II atoms, rather than implanting only Be ions as a p-type dopant of group II. It has been found that a deep impurity region with a gentle slope can be formed by ion implantation.

The present invention applies this to the formation of a guard ring.

On the other hand, when forming an n-type impurity region in the p-layer,
A similar effect can be obtained by using Si, a group (2) atom, as an n-type dopant and further ion-implanting P, a group V atom.

〔Example] An embodiment of the present invention will be described in detail with reference to the drawings.

The process of laminating layers on a substrate using a liquid phase epitaxy (LPE method) is the same as that explained in FIG.

The thickness of each layer and the concentration of impurities are as follows.

Thickness μm Concentration cm-'1:n"-In P substrate 350 1 Xl0
I82: n-InGaAsP light absorption layer 2 1 Xl
0163: n-LnP multiplication layer 1 1 XIO”
4: rl-1nP layer 25×101s, then
Using the SiO2 film or Si3N film as a mask, Cd is diffused into the light receiving region to form the p'-1nP layer 5. In the case of Cd diffusion, an extremely steep step-like junction can be obtained at the diffusion front.

The diffusion front may be in contact with the n-1nP multiplication layer 3, but a portion of the 1-1nP layer 4 may remain.

Next, as shown in FIG. 1(a), Be ions are implanted using the SiO□ film 7 that opens the guard ring region as a mask. The implantation energy is 150 KeV and the dose is 5.times.10"cm.sup.-".

Furthermore, ion implantation of A and l is performed subsequently. The implantation energy was 500 K e V and the dose was 5 XIO”c.
Let it be m-2.

The order of the Be and A1 ion implantations described above may be reversed.

By performing activation annealing on the ion-implanted portion, it is possible to form a guard ring 6 with a gradual and deep impurity concentration slope, as shown in FIG. 1 (al).

This completes the formation of the light-receiving element section, removes the SiO
The electrode 9 is made of Au/Zn/Au, and the n electrode 10 is made of AuGe.
Formed in This is shown in FIG. 1(b).

〔Effect of the invention〕

As explained above, by applying the method for manufacturing a photodetector of the present invention, a guard ring can be formed without significantly changing the conventional method, and a photodetector with a high breakdown voltage can be obtained.

[Brief explanation of drawings]

Figure 1 (al), (bl is a sectional view for explaining the method of manufacturing a light receiving element according to the present invention, Figure 2 (a), (bl is a sectional view for explaining the method of manufacturing a light receiving element according to the conventional technology) A cross-sectional view is shown. In the drawings, ■ is an n"-InP substrate, 2 is an n-1nGaAsP light absorption layer, 3 is an n-InP multiplication layer, 4 is an n--InP layer, and 5 is a p"-1nP layer. , 6 is a guard ring, 7 is a SiOZ film, 8 is a Si 3 N film, 9 is a p-electrode, and 10 is an n-electrode. h-angle cross-sectional view Fig. 1 + Q) @ Fig. 2

Claims (2)

[Claims] (1) In an APD using a III-V group compound semiconductor, forming a p-type guard ring (6) surrounding the light-receiving surface includes a step of ion-implanting a p-type dopant and a group III atom, respectively. A method for manufacturing a light receiving element characterized by: (2) In an APD using a III-V group compound semiconductor, forming an n-type guard ring surrounding the light-receiving surface includes a step of ion-implanting an n-type dopant and a group V atom, respectively. A method for manufacturing a light receiving element.