JPS616820A - Manufacture of compound semiconductor device - Google Patents

Abstract

PURPOSE:To form the PN junction in different depth through single diffusion to each InxGa1-xAsyP1-y layer by the thermal diffusion to the region including the interface of InxGa1-xAsyP1-y layers in different compositions, utilizing the fact that impurity diffusion rate to InxGa1-xAsyP1-y is different depending on the compositions x, y. CONSTITUTION:The InxGa1-xAsyP1-y layer 12 which becomes a photosensitive layer and InP layer are formed by epitaxial growth on the N type Inp substrate 11. Next, the InxGa1-xAsyP1-y layer 15 is selectively formed with the photosensitive region masked by adequate material 14 such as SiO2, Si3N4, etc. In this case, the planar surface can be formed by the melt-back in the case of LPE or by adequate etching in the case of the other growth method. After the mask 14 is removed, the P type regions 16, 17 are formed by the sealed tube thermal diffusion method with ZnP2 used as the diffusion source.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a compound semiconductor device, and more particularly to a method for thermally diffusing impurities.

Conventional Structure and Problems Compound semiconductors using GaAs or InP as substrates are used as light-receiving and emitting materials because their absorption wavelength range is in the infrared region used in optical communications. A photodiode or an avalanche photodiode is used as the light receiving element.

FIG. 1 is an explanatory diagram showing one configuration example of an avalanche photodiode.

InxGa, -Asyp, -y (○<z<1.o<, y layer 1) layer 2 which becomes a light-receiving layer on an n-type InP substrate 1
After epitaxially growing the InP layer 3 which becomes a region where avalanche multiplication occurs, a p-type head region 6 is formed to form a light receiving region 4. Formation of p region, Zn, Cd
Methods such as thermal diffusion, such as Be, Zn, Cd, etc., are used. However, in the manufacture of an avalanche photodiode, a step of forming the guard ring 6 is usually required. That is, in a pn junction without a guard ring, electric field concentration tends to occur at the junction end 7, and avalanche breakdown occurs quickly in other parts.

To prevent this, the p-type head area 6 is provided outside the light receiving area 4 with a shallow junction. By providing such a guard ring 6, the thickness σ8 of the InP layer under the light-receiving region can be made thinner than the thickness 9 of the InP layer under the guard ring region. Therefore, avalanche breakdown occurs in the light-receiving region 4. Occurs uniformly only within the body. Formation of such a guard ring requires two types of pn junctions with different junction depths, so two thermal diffusion and ion implantation steps are unavoidable. but,
In general, compound semiconductor surfaces are much more unstable than silicon and the like. InP, In, 2:Ga1-xA5 exposed to an atmosphere of f)ts○0~600''C due to thermal diffusion
Selective desorption of As and P on the yP1-y surface, surface oxidation,
Considering contamination, etc., it is of course better to minimize the number of high-temperature thermal diffusion steps. The same is true if you consider that an annealing step at 800 to 900° C. is required to recover crystallinity even if the shredded ion Y ten-nin process is used.

OBJECTS OF THE INVENTION The present invention solves the problems of the prior art, and provides a method for manufacturing a compound semiconductor device that can form pn junctions with two different diffusion depths σ in a single diffusion step. With the goal.

Structure of the Invention The present invention takes advantage of the fact that the impurity diffusion rate into Fi InxGa, -, AsyP, -y differs depending on the composition I and y,
Thermal diffusion is applied to the region including the interface of the ly layer, and each In
It is assumed that pn junctions of different depths are formed in the xGa, -air As, P1-y layers by one-time diffusion.

DESCRIPTION OF EXAMPLES FIG. 2 shows the InxGa1-air AS
A diagram of ZnO thermal expansion diffusion into y P 1- y is shown in deep water.

Figure 2 A [Non-doped InP, ZnP2 (1 mg/
cc) as a diffusion source and the diffusion depth was measured when thermal diffusion was carried out in a sealed tube. On the other hand, in Figure 2B, In(,,
53G4o, 47As under similar conditions to Zn(
7) It is a figure showing thermal diffusivity σ. Paying attention to the difference in the vertical axes in Figure 2 A and B, it can be seen that the ZnO thermal diffusion rate in InP is 2 to
It turns out that it is three times larger. Generally In-Ga, -Air As
As the composition approaches GaAs from InP at yP, -9, the diffusion rate slows down to that of Zn. Figure 2c (4) shows this situation.The larger the bandgap of In, 2:Ga1-fxAsyP1, which is lattice matched to InP, the closer the composition approaches InP,
This shows how the diffusion rate increases.

Based on this phenomenon, the present invention attempts to simultaneously form pn junctions with different diffusion depths σ in one diffusion by thermally diffusing layers with different diffusion rates.

FIG. 3 shows a manufacturing process diagram of an avalanche photodiode according to an embodiment of the present invention. InxGa1-, :AsyPl-y, which becomes a light-receiving layer on the n-type InP substrate 11.

(For example, J=0.53.,!/=1) Layer 12, InP
The layer 13 is epitaxially grown. Next vtc 5i0
2.

The light-receiving area is masked with a suitable material 14 such as Si3N4, and In xG a 1-xAs y P 1++
y (eg 1-0.27°I-0,60) layer 15 is selectively grown. At this time, by performing melt-back in the case of LPE or appropriate etching in the case of other growth methods before epitaxial growth, a planar surface as shown in FIG. 3B can be created. After removing the mask 14, p is removed by sealed tube thermal diffusion using ZnP2 as a diffusion source.
Forming mold regions 16,17. If we choose the conditions of diffusion temperature 550'C and diffusion time 15 minutes, the InP layer 16 will have about 3
．． 5117#, In0.73”'0.27AS0
, 60 po, , a p-type region with a depth of about 2.5 μm is formed in the lo layer 17.

Figure 4 shows the avalan/efodo diode manufactured in this manner. Since the depth of the diffusion region 16 in the light receiving region is formed deeper than the diffusion depth in the guard ring region formed by the region 17, edge breakdown is relaxed and avalanche breakdown occurs uniformly in the light receiving region 22.

In this way, by forming the guard ring by one-time diffusion, it is possible to reduce the high-temperature heat treatment process and manufacture a stable element with good reproducibility.

The present invention not only forms a guard ring of such an avalan/ephototer diode, but also forms a
It can be widely applied to P,y-based compounds. The present invention is shown in FIG.
This is another example in which the present invention is applied to a ng, 53 Gao, a7As 7 odd diode. n+ type InP substrate 1
In the non-doped InP layer 102 grown on 01,
Ino, ss GiLo, 47 As layer 1 with light receiving part
03 can be selectively grown. Here 5i02. Si3
Thermal diffusion of Zn is performed through a suitable diffusion mask 104 made of N4 or the like. When the conditions of diffusion temperature 5o○°C and diffusion time 15 minutes are adopted, 1.6 μm to 2 μm I
n0.53 can, 47 As heHO, 5~111
A junction with a depth of 1H is formed σJ. The photodiode thus produced is shown in FIG. 5B, and the deep diffusion layer 105 into InP acts as a channel stopper and has the effect of reducing dark current. Moreover, by adopting such a configuration, a stable pn junction with little variation can be obtained.

In the above embodiment, Zn was used as the diffusion impurity, but Cd, Mn, Mg, etc.
Of course, any impurity whose diffusion rate differs depending on the composition of A SyP, -y may be used as fX+/-1. Moreover, it can be applied not only to light-receiving elements but also to electric elements such as invat diodes.

The present invention is described in detail below.

This makes it possible to form pn junctions with different diffusion depths σ in a compound semiconductor device consisting of P and -y by a single thermal diffusion, and its practical value is extremely great.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an example of the configuration of a conventional avalanche photodiode, Figure 2 (A) is a diagram showing the depth of Zn diffusion into fiInP, Figure 2 (B) I-jxnO, 53c.
a[1,47As Zn) Diagram showing the diffusion depth, 2nd
Figure (C) QIn, Ga, -xAs, yP, -y
Figures 3 (A) to 3 (C) are diagrams showing the relationship between the band gap and the diffusion rate; FIGS. 5A and 5B are structural cross-sectional views of a photodiode according to another embodiment of the present invention. 21.107...Antireflection film, 20,108...
...n-side electrode, 19,109...n-side electrode, 18°1
04...Diffusion mask. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 TIME (mi, n) 1f JHEVe (secVt) 2nd Figure 1 E (7T'l 翔) TIME zo'z (secyB Figure 2) e, V) Figure 3

Claims (1)

[Claims] On the other hand, the first conductivity type In_xGa_1_-_xAs_y
P_1_-_y (0≦x≦1, 0≦y≦1) layer, and a second In_zGa_1_- having the same conductivity type as the In_xGa_1_-_xAs_yP_1_-_y layer but having a different composition.
_zAs_uP_1_-_u(0≦z≦1, 0≦u≦1
) layer, and the first In_xGa_1_-_xA
s_yP_1_-_y layer and second In_zGa_1_-
By applying thermal diffusion to the region including the interface of the _zAs_uP_1_-_u layer, the first In_xGa_1_-
In the _xAs_yP_1_-_y layer, the second In_zGa
_1_-_zAs_uP_1_-_u A method for manufacturing a compound semiconductor device characterized by forming a region of an opposite conductivity type deeper than the layer.