JP2996943B2 - Semiconductor light receiving device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light receiving device and a method of manufacturing the same, and more particularly, to a planar heterojunction avalanche photodiode having a guard ring structure.
(Avalanche PhotoDiode, hereinafter abbreviated as APD) and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a photodiode has been used as a detector for optical communication. Among them, an APD having an internal amplification function is useful in view of a margin on a receiving side. In particular, an APD using InGaAs or InGaAsP for the light absorption layer and using InP for the multiplication layer can perform a lattice-matched heterojunction and has a low loss region of 1.1 to 1.6 μm of the quartz optical fiber. Has reception sensitivity in the band. For this reason, it is promising as a detector for long-distance and large-capacity optical communication, and research and development thereof are being actively pursued.

[0003] An example of a conventional APD structure (Japanese Patent Laid-Open No. Sho 60-1)
9876) is shown in FIG. n ⁺ -InP substrate 81
N-InP buffer layer 82, n ^-- InGaAs
Light absorption layer 83, n-InGaAsP intermediate layer 84, nI
In a semiconductor multilayer film in which an nP avalanche multiplication layer 85 and an n ⁻ -InP layer 86 are sequentially formed, a light receiving region 87 of ap ⁺ type conductive region having a stepwise pn junction is formed by thermal diffusion or ion implantation. A first guard ring region 88 of a p-type conductive region having an inclined pn junction is formed around region 87 so as to partially overlap.

Further, a second guard ring region 89 having a shallower junction depth than the first guard ring region 88 is formed around the first guard ring region 88 so as to partially overlap. The first guard ring region 88 is for preventing the edge break of the step-type pn junction, and the second guard ring region 89 is for preventing the edge break of the first guard ring region 88. Incidentally, 91 is a transparent insulating film, 9
2 indicates an insulating film, and 93 and 94 indicate electrodes.

However, this type of APD has the following problems. That is, two guard rings require two ion implantation steps due to different formation conditions, and a high temperature (for example, 750 ° C.) for activation and diffusion thereof.
Requires a heat treatment step. In addition, since the pn junction alignment margin is set for each of the light receiving portion and the first and second guard ring portions, the pn junction area becomes larger than the diameter of the light receiving portion, which causes an increase in junction capacitance and dark current. I was

[0006]

As described above, the formation of the guard ring according to the prior art not only complicates the manufacturing process but also requires exposing the semiconductor substrate to a temperature higher than the epitaxial growth temperature for activating the implanted ions. It causes quality deterioration. Further, the dark current caused by the guard ring portion flows through the same electrode together with the dark current caused by the light receiving portion, which causes an increase in dark current.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to minimize the dark current of the light receiving section and to simplify the manufacturing process. An object of the present invention is to provide an apparatus and a method of manufacturing the same.

[0008]

Means for Solving the Problems (Constitution) The gist of the present invention is that the guard ring portion is formed by the
Instead of being formed so as to overlap with the outer periphery of the n-junction, it is formed simultaneously with the formation of the pn junction of the light-receiving unit in a region that does not overlap with the outer periphery of the light-receiving unit, and the light-receiving unit and the guard ring are connected to different electrodes. is there.

As described above, since APD is used by applying a high voltage, local break is likely to occur near the pn junction.
In order to suppress this, it is necessary to form a guard ring which is a gentle pn junction by ion implantation or the like. However,
According to studies and experiments conducted by the present inventors, it has been confirmed that a local break does not occur even when a high voltage is applied to an APD in which a guard ring is formed in a region where the outer peripheral portion of the light receiving unit does not overlap.

The present invention has been made in view of such a point. In a semiconductor light receiving device such as an APD, a semiconductor substrate of a first conductivity type, at least a light absorption layer laminated on the semiconductor substrate, and First including avalanche multiplication layer
Conductivity type and the semiconductor multilayer film, and the semiconductor film of a second conductivity type formed on the semiconductor multilayer film, from the surface to the semiconductor film
A high resistance region or a first conductivity type region is formed in a ring shape until reaching the back surface, and includes a separation region for electrically separating an inner light receiving region and an outer guard ring region. The light receiving region and the guard ring region are connected to different electrodes, respectively.

The present invention also provides a method for manufacturing a semiconductor light receiving device, comprising the steps of: forming at least an n-type light absorbing layer, an n-type avalanche multiplication layer, and a p-type same as the multiplication layer on an n-type semiconductor substrate.
A step of sequentially growing a p-type semiconductor layer and at least one of H, D, He, Li, Be, Ne, Ar, or n-type impurities between a region serving as a light receiving portion and a region serving as a guard ring portion of the p-type semiconductor layer. A step of ion-implanting one to separate a p-type light receiving region and a p-type guard ring region, and connecting different electrodes to each of the n-type semiconductor substrate, the p-type light receiving region and the p-type guard ring region And a step of performing

(Operation) According to the present invention, a guard ring formed to prevent a local break occurring near a pn junction to which a high electric field is applied is not provided by partially overlapping the outer periphery of a light receiving portion as in the conventional case. The light receiving section and the guard ring section are connected to different electrodes to independently apply a voltage, provided in a non-overlapping area on the outer periphery of the light receiving section. For this reason, the dark current caused by the guard ring portion does not flow to the light receiving portion.
As shown in (5), the dark current flowing in the light receiving section can be reduced. In the operating state, it is possible to suppress the occurrence of a high electric field extending in the lateral direction at the edge of the light receiving portion by the electric field of the independent guard ring portion, thereby preventing the step break pn junction edge break of the light receiving portion. It becomes possible.

Further, by forming the opposite conductivity type semiconductor layer during the growth of the semiconductor crystal and separating the light receiving portion and the guard ring portion by ion implantation, even a thermal diffusion process is not necessarily required. Accordingly, a semiconductor light receiving device that has a simple manufacturing process, can minimize the thermal fluctuation of the crystal due to the low temperature of the process, and can reduce the dark current can be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. In the following embodiment, I
Although an nP / InGaAs heterojunction APD will be described, it is easily understood that the same applies to other heterojunction APDs and homojunction APDs.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
It is sectional drawing which shows schematic structure of APD concerning embodiment of 1st Embodiment.

On an n ⁺ -InP substrate 11, an n-InP buffer layer 12 is formed to have a thickness of 2 μm and a carrier concentration of 1-2 × 1.
The n-InGaAs light absorbing layer 13 of 0 ¹⁵ cm ^-3 is made 2 μm thick and the n-InGaAs having a carrier concentration of 2 × 10 ¹⁶ cm ^-3.
The sP intermediate layer 14 has a thickness of 0.4 μm and a carrier concentration of 2 to
3 × 10 ¹⁶ cm ⁻³ n-InP avalanche multiplication layer 15
Is formed to a thickness of 1 μm, and an n ⁻ -InP layer 16 having a carrier concentration of 1 to 2 × 10 ¹⁵ cm ⁻³ is formed to a thickness of 0.8 μm by epitaxial growth, and then Cd is deposited to 560 using the SiO ₂ film 21 as an insulating mask. Heat diffusion at a temperature of ℃ for 15 minutes,
The p ⁺ -type light receiving region 17 and the guard ring region 18 were formed such that the pn junction was located at a desired depth. Ohmic electrodes 22 and 23 were formed on a part of the surface of the light receiving region 17 and on the surface of the guard ring region 18 so that they could be taken as separate electrodes, and an ohmic electrode 24 was formed on the back side of the substrate 11.

In this embodiment, since no ion implantation is performed, a high-temperature heat treatment for activation is not required.
FIG. 2 shows lines of electric force in the depletion layer when a high voltage is applied to the APD according to this embodiment. In FIG. 2, the absolute value of the voltage applied to the substrate is smaller in the guard ring region 18 than in the light receiving region 17. In this case, the current caused by the guard ring region 17 is
7 flows into the electrode 23 formed on the light receiving region 17.
Can be kept low. Further, a high electric field extending in the lateral direction at the edge of the light receiving region 17 can be suppressed by the electric field formed by the guard ring region 18, and as a result, the edge break of the step-type pn junction in the light receiving region 17 can be prevented. .

Thus, according to the present embodiment, the light receiving region 1
In the three-terminal structure APD having the structure in which the guard ring 7 and the guard ring region 18 are separated from each other, the effect of preventing the local break is sufficiently obtained, and the dark current caused by the guard ring region 18 is reduced by the electrode formed on the guard ring region 18. 23, the dark current flowing through the main electrode 21 formed on the light receiving region 17 can be reduced. Moreover, a semiconductor light receiving device having good element characteristics can be realized by a low-temperature process with a simplified manufacturing process. Therefore,
A semiconductor light receiving device having excellent element characteristics can be easily realized with good reproducibility, and its usefulness is enormous.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
It is sectional drawing which shows the schematic structure of APD which concerns on embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the n ⁺ -InP substrate 11
After forming each of the layers 12 to 16 under the same conditions as in the previous embodiment, Be ions are applied to the outer periphery of a region to be a guard ring at 150 kV at 1 × 10 5 using a SiO ₂ film (not shown) as an insulating mask. Inject ¹³ cm ^-2 and 20 at 700 ° C
By performing heat treatment for minutes, activation and diffusion after ion implantation are performed, a guard ring region (second guard ring region) 19 is formed, and after removing the SiO ₂ film for ion implantation, heat is newly added. An SiO ₂ film 21 is formed as an insulating mask for diffusion, and Cd is deposited at a temperature of 560 ° C. for 15 minutes.
The light receiving region 17 and the guard ring region (first guard ring region) 18 were formed so that the p ⁺ n junction was located at a desired depth.

The structure shown in FIG. 3 corresponds to the guard ring region 1 shown in FIG.
The structure is such that ions are implanted in the outer peripheral portion of the guard ring region 8 so that a voltage can be applied to the guard ring region 18 with a voltage approximately equal to or slightly higher than the voltage applied to the light receiving region 17.

FIG. 4 shows lines of electric force when a high voltage is applied to the APD according to the second embodiment. In FIG. 4, the absolute value of the voltage applied between the guard ring region 18 and the light receiving region 17 is slightly larger or almost the same as that of the light receiving region 17. Also in this case, the electric field formed by the guard ring region 18 can suppress the generation of a high electric field extending in the lateral direction at the edge of the light receiving region 17, whereby the electric field from the light receiving portion pn junction is reduced from the avalanche multiplication layer. Since the current uniformly extends to the light absorption layer, and the current caused by the guard ring region 18 flows to the electrode 23 formed on the guard ring region 18 as in the first embodiment, the darkness of the light receiving region 17 is reduced. The current can be kept low.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention.
It is sectional drawing which shows the schematic structure of APD which concerns on embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the n ⁺ -InP substrate 11
After the layers 12, 15 are formed under the same conditions as in the previous embodiment, the carrier concentration is then reduced to 1-2 × 10 ¹⁵ c.
The n ⁻ -InP layer 16 of m ^{−3 has} a thickness of 0.2 μm, and the p ⁺ -InP layer 56 having a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ has a thickness of 0.8 μm.
It was formed to a thickness of μm by epitaxial growth. Then, using the SiO ₂ film 21 as an insulating mask, H ions were implanted at 1 × 10 ¹³ cm ⁻² at 100 kV to form an insulating portion (high resistance layer) 58 for separating the light receiving region 17 and the guard ring region 18. . This ion-implanted p-type InP
The region 56 has a resistivity of 10 ⁶ Ω by heat treatment at about 400 ° C.
cm or more. Although hydrogen is used as an ion implantation source in FIG. 5, an n-type impurity may be used instead. In this case, if heat treatment for activation is performed after ion implantation of the n-type impurity, a gentle pn junction is formed at the interface between the p ⁺ -type light receiving region 17 and the ion implantation region, and the electric field concentration is alleviated. Can be expected.

FIG. 6 shows lines of electric force when a high voltage is applied to the APD according to the third embodiment. In FIG. 6, the absolute value of the voltage applied to the substrate is substantially the same in the light receiving region 17 and the guard ring region 18.

The present invention is not limited to the above embodiments. In the embodiment, InP / InGaAs is used.
Although the s heterojunction APD has been described, the invention can be applied to other heterojunction APDs, homozygous APDs, and the like.
That is, instead of using a semiconductor multilayer film, it is also possible to form a light receiving region or a guard ring region directly on a surface layer of a substrate such as germanium or silicon. In addition, various modifications can be made without departing from the scope of the present invention.

[0027]

As described above in detail, according to the present invention, the guard ring is not formed so as to be superposed on the outer peripheral portion of the pn junction of the light receiving portion, but is formed in a region not overlapping with the outer peripheral portion of the light receiving portion. By forming the pn junction at the same time as forming the pn junction and connecting the light receiving portion and the guard ring portion to different electrodes, the dark current flowing through the electrodes formed on the light receiving portion can be suppressed low. In addition, by separating the light receiving portion and the guard ring portion by ion implantation, a subsequent heat diffusion process is not required, and the light receiving portion and the guard ring portion can be formed simultaneously by one ion implantation process. It can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic structure of an APD according to a first embodiment.

FIG. 2 is a schematic diagram illustrating lines of electric force when a voltage is applied to the APD according to the first embodiment.

FIG. 3 is a sectional view showing a schematic structure of a second embodiment.

FIG. 4 is a schematic diagram illustrating electric lines of force according to a second embodiment.

FIG. 5 is a sectional view showing a schematic structure of a third embodiment.

FIG. 6 is a schematic diagram showing electric lines of force according to a third embodiment.

FIG. 7 is a characteristic diagram showing dark current characteristics of an APD of the present invention and a conventional APD when a reverse voltage is applied.

FIG. 8 is a sectional view showing a schematic structure of a conventional APD.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... n ⁺ -InP board 12 ... n-InP buffer layer 13 ... n-InGaAs light absorption layer 14 ... n-InGaAsP intermediate layer 15 ... n-InP avalanche multiplication layer 16 ... n ^-- InP layer 17 ... p ⁺ type Layer (light receiving area) 18 p ⁺ -type layer (first guard ring area) 19 p ⁺ -type layer (second guard ring area) 21 insulating film 22, 23 p-side electrode 24 n-side electrode 56 ... p ⁺ -InP layer 58 ... insulating part (high resistance layer)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-173882 (JP, A) JP-A-56-87380 (JP, A) JP-A-50-57785 (JP, A) JP-A-63-1988 204666 (JP, A) JP-A-63-224268 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/10-31/113

Claims (2)

(57) [Claims] A semiconductor substrate of a first conductivity type, a semiconductor multilayer film of a first conductivity type including at least a light absorption layer and an avalanche multiplication layer laminated on the semiconductor substrate, and The formed second conductivity type semiconductor film, and a high resistance region or
A first conductive type region becomes formed in a ring shape, to electrically isolate the inner light receiving region and an outer guard ring region min
A semiconductor light receiving device comprising: a separation region ; wherein the light receiving region and the guard ring region are respectively connected to different electrodes. 2. A step of sequentially growing at least an n-type light absorbing layer, an n-type avalanche multiplication layer and a p-type semiconductor layer of the same kind as the multiplication layer on an n-type semiconductor substrate; H, between the region to be the part and the region to be the guard ring part
Ion-implanting at least one of D, He, Li, Be, Ne, Ar, or an n-type impurity to separate a p-type light receiving region and a p-type guard ring region; connecting different electrodes to the p-type light receiving region and the p-type guard ring region, respectively.