JP2776228B2 - Manufacturing method of semiconductor light receiving element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to optical communication, optical information processing,
The present invention relates to a method for manufacturing a semiconductor light receiving element used for optical measurement and the like.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor light receiving element for optical communication in the 1 to 1.6 μm band, an InP lattice-matched on an InP substrate has been used.
_0.53 Ga _0.47 PIN type semiconductor light-receiving element As layer (hereinafter referred to as InGaAs layer) and the light-absorbing layer ( "optical communication element engineering", Yonezu Mr. al., Engineering books, Inc. published, 371 pp. (19
83)), an avalanche multiplication type semiconductor light receiving element (Electronic Letters (Electronic)
s Letters) 1984, 20 volumes, pp653
-654). Particularly, the latter is practically used for long-distance communication because it has an internal gain effect and a high-speed response due to avalanche multiplication.

In recent years, in avalanche multiplication semiconductor light receiving devices, a superlattice APD (avalanche multiplication semiconductor light receiving device, in which a superlattice structure is applied to a multiplication layer to promote ionization of electrons by conduction band discontinuous energy, has been proposed. Below AP
Abbreviated as D. ) Will be studied. Particularly, in a superlattice APD using an InAlAs / InAlGaAs superlattice layer as a multiplication layer, a gain bandwidth product of 120 GHz has been reported (I-I-I-I-).
Photonics Technology Letters (IEEE
photonics TechnologyLette
rs), 1993, vol. 5, pp. 675-677). Figure 7 shows a typical InAlAs / InAlGaAs superlattice APD.
FIG. FIG. 8 shows a conventional manufacturing method. First, n ⁺ is formed on an n-type InP substrate 1 by a vapor phase growth method.
-Type InP buffer layer 2, n ⁺ -type InAlAs buffer layer 3, n ^-- type InAlAs / InAlGaAs superlattice multiplication layer 4, p ⁺ -type I
nP electric field relaxation layer 5, p ⁻ -type InGaAs light absorption layer 6, p
^{A +} type InP cap layer 7 and ap ⁺ type InGaAs cap layer 8 are sequentially laminated. Thereafter, a mesa is formed with a Br-based etchant, and SiN _x is deposited on the surface as a passivation film 9. Thereafter, ohmic electrodes are deposited on the n-side 10 and the p-side 11 to complete the process. The incident light 12 enters from the surface.

[0004]

As described in the Background of the Invention, the superlattice APD is formed as a mesa by etching with a Br-based etchant, and a nitride film is used as a passivation film. However, it is known that the formation of a mesa by wet etching has poor uniformity over a large area, and it is easy to form defects or trap levels of carriers on the etched side surface. On the other hand, mesa formation by selective growth is also conceivable to avoid etching, but in normal selective growth, atoms flying on the mask migrate in the horizontal direction, so that growth occurs near the interface between the mask edge and the growth surface. It causes accelerated, so-called ridge growth.

Further, in the case of a passivation film such as a nitride film or an oxide film, the bond with the semiconductor layer is not completely bonded, so that there is no reliability over time and a surface dark current is caused.

An object of the present invention is to solve the above-mentioned problems and to provide a highly uniform and highly reliable semiconductor light receiving element.

[0007]

According to the present invention, there is provided a method of manufacturing a semiconductor light receiving device in which a laminated portion such as a light absorbing layer is formed on a semiconductor substrate by using selective growth. The passive surface of the semiconductor light-receiving element.
Selective growth up to the solution film .

[0008]

Further, the passivation film has a high resistance I
It is characterized by being nAlAs.

[0010]

FIG. 1 is a view for explaining the principle of the method for manufacturing a semiconductor light receiving element according to claim 1 of the present invention. Normally, when performing selective growth, all parts other than the laminated portion are covered with a mask. This mask is made of SiO ₂ or SiN _x
Etc. are used. In the case of this method, as shown in FIG. 1A, the mask width is increased to about 100 μm or more, and the atoms flying on the mask migrate in the horizontal direction. As a result, the growth is accelerated near the interface between the mask edge and the growth surface, causing so-called ridge growth, and it becomes difficult to control the film thickness. On the other hand, according to the manufacturing method of the first aspect of the present invention, the mask width is set to 0.5 μm or less (FIG. 1B).
Therefore, the total amount of atoms flying on the mask is small, and the ridge growth can be prevented.

FIG. 6 shows the relationship between the mask width and the ridge height.
Since the selective growth width is as large as 50 μm, ridge growth is inevitable when a normal selective growth mask is used. However, as shown in the figure, the ridge height is reduced by reducing the mask width W. By setting the ridge height to 10% or less of the height of the flat growth portion, excellent device characteristics can be obtained.

Since the mask is made smaller, a semiconductor layer is also formed in a region that is not originally required. However, if the mask is removed, the insulating property is ensured, and there is no problem at all.
Moreover, according to this method, a mesa can be formed without etching, so that a high-quality mesa structure without damage to the mesa wall surface due to the etching can be obtained. in addition,
In-plane unevenness due to wet etching is eliminated,
A highly uniform mesa structure can be obtained over a large area. The method for manufacturing a semiconductor light receiving element according to claim 2 of the present invention comprises:
A mesa structure is formed by selective growth using a narrow mask, and a passivation film is subsequently formed. In this method, the structure of FIG. 2 can be formed by one growth. Therefore, the surface of the cap layer does not need to be exposed to the air before the growth of the passivation film, and there is an advantage that the passivation film can be formed on the clean surface. As a result, defects and carrier trap levels formed at the interface between the passivation film and the cap layer can be significantly reduced as compared with the device obtained by the conventional manufacturing method, thereby suppressing the occurrence of leak current and improving reliability. Can be. Further, since it can be formed by one growth, the number of manufacturing steps can be reduced.

Next, the operation of claim 3 of the present invention will be described. Usually, a polycrystalline film such as SiO ₂ or SiN _x is used as a surface passivation film of a semiconductor light receiving element having a mesa structure. However, in these films, the bond bonding with the single crystal semiconductor surface layer is not perfect,
This is also a cause of surface leakage current generation and temporal deterioration of reliability. In order to solve these problems, the present invention proposes to use high-resistance single crystal InAlAs. I
In the case of nAlAs, the above problem is solved because it is a single crystal film. In addition, InAlAs has a wide bandgap and does not absorb light having a wavelength in the 1.3 μm or 1.55 μm band used for optical communication. As a method for growing high-resistance InAlAs, there is also a method of doping Fe. FIG.
Shows the V / III ratio dependence of the concentration of Zn-doped InAlAs. It can be seen that Zn is a p-type dopant, but exhibits high resistance characteristics when the V / III ratio is reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 4 is a diagram for explaining a manufacturing method process according to one embodiment of the present invention. A resist 13 is applied on the semiconductor substrate, and lift-off is performed only on a portion where a mask is deposited (FIG. 4A). Next, chemical vapor deposition (CV)
D) to deposit SiO ₂ 14 (FIG. 4B). At this time, the SiO ₂ mask width was 0.5 μm. Next, after the resist is lifted off (FIG. 4C), the superlattice APD
The structure is grown by MOVPE (FIG. 4D). The structure is such that an n ⁺ -type InP buffer layer 2 is formed on an n-type InP substrate 1.
Is 0.1 μm and the n ⁺ -type InAlAs buffer layer 3 is 0.1 μm.
1 μm, n ⁻ -type InAlAs / InAlGaAs superlattice multiplication layer 4
2 μm, p ⁺ type electric field relaxation layer 5 at 500 A, p ⁻ type light absorption layer 6 at 1.2 μm, p ⁺ type InP cap layer 7 at 0.2 μm
μm and p ⁺ -type InGaAs contact layer 8
m are sequentially laminated. Thereafter, the SiO ₂ mask is removed to complete the mesa structure (FIG. 4E).

FIG. 5 shows a second embodiment of the present invention.
This will be described in detail with reference to FIG. Resist 13 on semiconductor substrate
Is applied and lift-off is performed only on the portion where the mask is to be deposited (FIG. 5A). Next, S is deposited by chemical vapor deposition (CVD).
iO ₂ 14 is deposited (FIG. 5B). At this time, Si
The O ₂ mask width was 0.5 μm. Next, after the resist is lifted off (FIG. 5 (c)), the superlattice APD structure is
It grows by PE method (FIG. 5 (d)). The structure is an n-type I
An n ⁺ -type InP buffer layer 2 is formed on an nP substrate 1 by 0.1 μm.
m, n ⁺ type InAlAs buffer layer 3 is 0.1 μm, n
^- type InAlAs / InAlGaAs superlattice multiplication layer 4 of 0.2 [mu] m, p
^{The +} type electric field relaxation layer 5 is 500 A, and the p ⁻ type light absorption layer 6 is 1.A.
2 μm, the p ⁺ -type InP cap layer 7 is
⁺ -Type InGaAs contact layers 8 are sequentially laminated by 0.1 μm. Subsequently, Zn is added under the condition of a V / III ratio of 100.
A doping InAlAs 15 is grown (FIG. 5E).
The Zn doping amount at this time is [DEZn] / [III]
The ratio was 0.27. Under these conditions, high resistance InAl
An As epi-passivation film was produced. After this, Si
The mesa structure is completed by removing the O ₂ mask (FIG. 5 (f)
).

[0016]

The method of manufacturing a semiconductor light receiving element according to the present invention is characterized in that a mesa structure is formed by selective growth using a narrow mask and high-resistance InAlAs epi-passivation is used. The former effect is that defects or carrier trap levels are prevented from being formed on the mesa surface due to wet etching, and the in-plane uniformity can be greatly improved. The latter effect is in that the bond between the interface of the semiconductor layer and the passivation film is strengthened, thereby suppressing leakage current and improving reliability.

Further, in the manufacturing method employing both of them, the growth up to the epi-passivation can be performed by a single growth, the number of manufacturing steps can be reduced, and the passivation film can be formed without exposing the semiconductor surface to the atmosphere. Obtainable.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the invention of claim 1;

FIG. 2 is a structural diagram of a semiconductor light receiving element.

FIG. 3 is a diagram showing a relationship between a Zn doping concentration and a V / III ratio.

FIG. 4 is a diagram for explaining the embodiment of claim 1;

FIG. 5 is a diagram for explaining an embodiment of claim 2;

FIG. 6 is a diagram illustrating a relationship between a mask width and a ridge height.

FIG. 7 is a structural diagram of a conventional superlattice APD.

FIG. 8 is a diagram showing a conventional method for manufacturing a semiconductor light receiving element.

[Explanation of symbols]

Reference Signs List 1 n-type InP substrate 2 n ⁺ -type InP buffer layer 3 n ⁺ -type InAlAs buffer layer 4 n ^-- type InAlAs / InAlGaAs superlattice multiplication layer 5 p ⁺ -type InP electric field relaxation layer 6 p ^-- type InGaAs light absorption layer 7 p ⁺ Type InP cap layer 8 p ⁺ type InGaAs contact layer 9 SiN _x passivation film 10 n-side ohmic electrode 11 p-side ohmic electrode 12 incident light 13 resist 14 SiO ₂ passivation film 15 InAlAs epi passivation film

Claims (2)

(57) [Claims] 1. A method of manufacturing a semiconductor light receiving element formed by using a selective growth stacked portion of the light-absorbing layer or the like on a semiconductor substrate, the mask width of the selective growth and 0.5μm or less, half
Selective growth up to surface passivation film of conductor photo detector
A method for manufacturing a semiconductor light receiving element. 2. The method according to claim 1, wherein the passivation film has a high resistance InA.
2. The method according to claim 1 , wherein 1As is used.