JPH02262379A - Semiconductor photodetector and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture an APD, etc., capable of minimizing the dark current at a photodetecting part as well as simlifying the manufacturing processes by a method wherein a guard ring regions are formed encircling the photodetecting region not to be overlapped therewith and then the photodetecting region and the guard ring regions are connected respectively to different electrodes. CONSTITUTION:The title semiconductor photodetector is provided with the first conductivity type semiconductor substrates 11 to 16, the second conductivity type photodetecting region 17 formed on the surface layer 16 of the semiconductor substrates 11 to 16, guard rings 18 formed encircling the said photodetecting region 17 not to be overlapped with the region 17 while the said photodetecting region 17 and the guard ring regions 18 are connected respectively to different electrodes 22, 23. For example, an n-InP buffer layer 12, an b-InGaAs photoabsorption layer 13, an n-InGaAsP intermediate layer 14, an n-InP avalanche duplicated layer 15 and an n-InP layer 16 are successively and epitaxially deposited on an n<+>InP substrate 11 and then Cd is thermally diffused using an SiO2 film 21 as a mask so as to form the p<+>type photodetecting region 17 and the guard ring regions 18.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a semiconductor light receiving device and a method for manufacturing the same.
In particular, the Brehner-type heterojunction avalanche photodiode (Avalanche P) with a guard ring structure
The present invention relates to a semiconductor light receiving device such as a photo diode (hereinafter abbreviated as APD) and a method for manufacturing the same.

(Prior Art) Conventionally, photodiodes are generally used as detectors for optical communication, but among them, APDs having an internal amplification function are useful from the viewpoint of margin on the receiving side. especially,
Using InGaAs or InGaAsP for the light absorption layer,
An APD using InP as a multiplication layer is capable of forming a lattice-matched heterojunction, and has reception sensitivity in the 1.1-1.6 μm band, which is the low-loss region of silica-based optical fibers. Therefore, it is promising as a detector for long-distance, high-capacity optical communication.
Research and development is actively underway.

An example of a conventional APD structure (Japanese Patent Application Laid-Open No. 60-19878fi
(No.) is shown in Figure 8. n”-1nP substrate 81
1nP buffer layer 82. n--InGaAs light absorption layer 8
3. n-InGaAsP intermediate layer 84. A light-receiving region 87 of a p+ type conductive region having a stepped pn junction is formed in a semiconductor multilayer film in which an n-InP avalanche multiplication layer 85 and an n--InP layer 86 are sequentially formed by thermal diffusion or ion implantation. A first guard ring region 88, which is a p-type conductive region having a sloped pn junction, is formed around the light receiving region 87 so as to partially overlap with the first guard ring region 88. Further, a first guard ring region 88 is formed around the first guard ring region 88.
A second guard ring region 89 having a shallower junction depth is formed so as to partially overlap. The first guard ring region 88 prevents edge break of the stepped pn junction, and the second guard ring region 89 serves as the first guard ring region 8.
This is to prevent the edge break of 8. In addition, 9
1 is a transparent insulating film, 92 is an insulating film, and 93 and 94 are electrodes.

However, this type of APD has the following problems. That is, since the two guard rings have different formation conditions, two ion implantation steps are required, and a high temperature (for example, 750° C.) heat treatment step is required for activation and diffusion.

In addition, for the light receiving section, the first and second guard ring sections,
In order to provide a margin for alignment of each pn junction, the pn junction area becomes larger than the diameter of the light receiving portion, leading to an increase in junction capacitance and dark current.

(Problems to be Solved by the Invention) In this way, forming a guard ring using the conventional technology not only requires a complicated manufacturing process, but also requires exposing the semiconductor substrate to a higher temperature than the epitaxial growth temperature in order to activate the implanted ions. This may cause quality deterioration. Furthermore, the dark current caused by the guard ring portion flows through the same electrode as the dark current caused by the light receiving portion, which causes an increase in dark current.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a semiconductor light receiving device and its semiconductor light receiving device that can minimize the dark current in the light receiving section and simplify the manufacturing process. The purpose is to provide a manufacturing method.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is that the guard ring portion is not formed overlapping the outer peripheral portion of the pn junction of the light receiving portion, but is formed in an area that does not overlap with the outer peripheral portion of the light receiving portion. The method is to form the pn junction simultaneously with the formation of the pn junction of the light receiving part, and to connect the light receiving part and the guard ring part to different electrodes.

As mentioned above, since APD is used by applying high voltage, p
Local breakage tends to occur near the n-junction, and in order to suppress it, it is necessary to form a guard ring, which is a gentle pn junction, by ion implantation or the like. However, according to research and experiments conducted by the present inventors, it has been confirmed that local breakage does not occur even when a high voltage is applied to an APD in which a guard ring is formed in a non-overlapping area of the outer periphery of the light receiving part.

The present invention focuses on such points, and includes a semiconductor substrate of a first conductivity type, a light-receiving region of a second conductivity type formed on a surface layer of the semiconductor substrate, and a light-receiving region formed on the surface layer of the semiconductor substrate. The present invention proposes a three-terminal semiconductor light receiving device including a guard ring region formed so as not to overlap the surrounding light receiving region, and in which the light receiving region and the guard ring region are respectively connected to different electrodes.

The present invention also provides a method for manufacturing a semiconductor light receiving device, in which impurities of a second conductivity type are introduced into the surface layer of a semiconductor substrate of a first conductivity type, and a light receiving region of a second conductivity type and a second conductive region surrounding the light receiving region are provided. In this method, a guard ring region of the mold is formed at the same time, and then different electrodes are connected to the light receiving region and the guard ring region, respectively.

(Function) According to the present invention, the guard ring formed in order to prevent local breakage that occurs near the pn junction where a high electric field is applied is not provided partially overlapping the outer periphery of the light receiving part as in the conventional method, but instead of providing a guard ring around the outer periphery of the light receiving part. The light-receiving part and the guard ring part are connected to different electrodes and voltages are applied independently. Therefore, dark current caused by the guard ring portion does not flow to the light receiving portion, and the dark current flowing to the light receiving portion can be reduced as shown in FIG. 7. In addition, in the operating state, the electric field of the independent guard ring part can suppress the generation of a high electric field extending in the lateral direction at the edge of the light receiving part, thereby preventing the edge break of the stepped pn junction in the light receiving part. It becomes possible.

Furthermore, the light receiving part and the guard ring part can be formed by one-time thermal diffusion without aligning the pn junction as in the conventional method, and there is no need for high-temperature processes such as heat treatment after ion implantation. do not. Moreover, if a semiconductor layer of opposite conductivity type is formed during semiconductor crystal growth and the light receiving part and the guard ring part are separated by ion implantation, even a thermal diffusion process is not necessarily required. Therefore, it is possible to obtain a semiconductor light-receiving device that has a simple manufacturing process, can minimize thermal fluctuations in the crystal by lowering the process temperature, and can also achieve low dark current.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

In the following examples, InP/InGaAs heterojunction APD will be explained, but other heterojunction APDs will be described.
It is easily understood that the same holds true for D, homozygous APD, and the like.

FIG. 1 is a sectional view showing a schematic structure of an APD according to a first embodiment of the present invention. On the n''-InP substrate 11, n
The -1nP buffer layer 12 is 2 am thick, and the n-1n GaAs light absorption layer 13 with a carrier concentration of 1 to 2 x 10''c+n -' is 2 am thick, and the carrier concentration is 2 x 10
The n-1nGaAsP intermediate layer 14 of 11016a is 0.4
μm thick, carrier concentration is 2-3 x 10110l6
'n-1nP avalanche multiplier layer 15 with a thickness of 1 μm,
n−1 with a carrier concentration of 1 to 2 × 10” cm−1
After forming the nP layer 16 to a thickness of 0.8 μm by sequential epitaxial growth, using the 5in2 film 21 as an insulating mask, Cd was thermally diffused at a temperature of 560° C. for 15 minutes so that the pn junction was located at the desired depth. A p+ type light receiving region 17 and a guard ring region 18 were formed. In addition, light receiving area 1
7 and the surface of the guard ring region 18, ohmic electrodes 22.
23 was formed, and further an ohmic electrode 24 was formed on the back side of the substrate 11.

In this embodiment, high-temperature heat treatment for activation is not required because it is not performed after ion implantation. FIG. 2 shows lines of electric force within 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 between the guard ring region 18 and the substrate is smaller than that of the light receiving region 17. In this case, since the current caused by the guard ring region 17 flows to the electrode 23 formed on the guard ring region 17, the dark current in the light receiving region 17 can be suppressed to a low level.

Further, the electric field formed by the guard ring region 18 can suppress a high electric field extending laterally at the edge of the light receiving region 17, and as a result, edge breakage of the stepped pn junction in the light receiving region 17 can be prevented. .

Thus, according to this embodiment, in a three-terminal APD having a structure in which the light receiving region 17 and the guard ring region 18 are separated, the effect of preventing local breakage is sufficiently obtained, and the dark current caused by the guard ring region 18 is reduced. Since the dark current flows through the electrode 23 formed on the guard ring region 18, the dark current flowing through the main electrode 21 formed on the light receiving region 17 can be suppressed to a low level. Furthermore, a semiconductor light receiving device having good device characteristics can be realized by a low-temperature process that simplifies the manufacturing process. Therefore, a semiconductor light-receiving device with excellent device characteristics can be easily realized with good reproducibility, and its usefulness is enormous.

FIG. 3 is a sectional view showing a schematic structure of an APD according to a second embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, on the n'' I n P substrate 11,
Each layer 12. ~, 16 were formed under the same conditions as in the previous example, and then Be ions were applied to the outer periphery of the region that would become the guard ring at a rate of 150K using a SiO2 film (not shown) as an insulating mask.
By implanting IX 1013c111-2 at V and performing heat treatment at 700° C. for 20 minutes, activation and diffusion after ion implantation are performed to form a guard ring region (second guard ring region) 19, and the ion implantation is performed. After removing the SiO2 film 21 for heat diffusion, a new SiO2 film 21 is removed for heat diffusion.
was formed as an insulating mask, and Cd was heated to 1 at a temperature of 560°C.
Thermal diffusion was carried out for 5 minutes to form a light receiving region 17 and a guard ring region (first guard ring region) 18 such that the p + n junction was located at a desired depth.

The structure shown in FIG. 3 is a structure in which ions are implanted into the outer periphery of the guard ring region 18 shown in FIG. This allows a high voltage to be applied to the FIG. 4 shows an AP according to a second embodiment of the present invention.
The lines of electric force when a high voltage is applied to D are shown. In Fig. 4, the absolute value of the voltage applied between the substrate and the light receiving area 1 is
7, the guard ring region 18 is slightly larger or about the same size.

In this case as well, the electric field formed by the guard ring region 18 can suppress the generation of a high electric field extending laterally at the edge of the light receiving region 17.
The electric field from the n-junction now extends uniformly from the avalanche multiplication layer to the light absorption layer, and as in the first embodiment, the current caused by the guard ring region 18 is formed on the guard ring region 18. Since the dark current flows through the electrode 23, the dark current in the light receiving region 17 can be kept low.

FIG. 5 is a sectional view showing a schematic structure of an APD according to a third embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, each layer 1 is placed on the ri"-InP substrate 11.
2. ~, 15 were formed under the same conditions as in the previous example, and then
Next, n− with a carrier concentration of 1 to 2×10”cn+−′
-1nP layer 16 is 0.2 μm thick, carrier concentration is I
X 10110l8'p''-1nP layer 56 is 0.8μ
It was formed by sequential epitaxial growth to a thickness of m. Next, using the 5 in 2 film 21 as an insulating mask, ions were implanted at 100 kV TE I x 10''ell-2 to form an insulating part (high resistance layer) 58 for separating the light receiving region 17 and the guard ring region 18 . This ion-implanted p-type 1nP region 56 becomes a semi-insulating region 58 with a resistivity of 106Ω (up to) or more by heat treatment at about 400°C.
Although hydrogen is used as the ion implantation source in FIG. 5, n-type impurities may be used instead. In this case, if heat treatment for activation is performed after ion-implanting the n-type impurity, a gentle p-n junction will be formed at the interface between the p4-type light-receiving region 17 and the ion-implanted region, and the electric field concentration will be relaxed. You can expect it.

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

Note that the present invention is not limited to the embodiments described above. In the example, I n P / I n GaAs
Although the description has been made regarding heterozygous APD, the present invention can also be applied to other heterozygous 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 and a guard ring region directly on the surface layer of a substrate made of germanium, silicon, or the like. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, the guard ring portion is not formed overlapping the outer peripheral portion of the pn junction of the light receiving portion, but the light receiving portion is formed in an area that does not overlap with the outer peripheral portion of the light receiving portion. By forming the pn junction simultaneously with the formation of the pn junction and connecting the light receiving part and the guard ring part to different electrodes, the dark current flowing through the electrode formed on the light receiving part can be suppressed to a low level. Furthermore, since the pn junction of the light receiving part and the pn junction of the guard ring part can be formed in one diffusion process, the manufacturing process can be simplified.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a schematic structure of an APD according to a first embodiment of the present invention, FIG. 2 is a schematic diagram showing lines of electric force when voltage is applied to the APD of the first embodiment, and FIG. 3 is a cross-sectional view showing the schematic structure of the second embodiment of the present invention, FIG. 4 is a schematic diagram showing the lines of electric force in the second embodiment, and FIG. 5 is a schematic diagram of the third embodiment of the present invention. 6 is a schematic diagram showing the lines of electric force in the third embodiment; FIG. 7 is a characteristic diagram showing the dark current characteristics of the APD of the present invention and the conventional APD when reverse voltage is applied. , FIG. 8 is a cross-sectional view showing the schematic structure of a conventional APD. 11-n''-1n P substrate, 12-n-1n P
Rose fluorine layer, 13...n-1nGaAs light absorption layer, 1
4--・n-I n Ga As P middle layer, 1
5-n -1, nP avalanche multiplication layer, 16...n
--InP layer, 17...p+ type layer (light receiving area) 18
...p1 type layer (first guard ring region), 19...
・p+ type layer (second guard ring region), 21... insulating film, 22.23... p side electrode, 24... n side electrode, 56-p''-1nP layer, 58-... Insulating part (high resistance layer). Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 5 Figure 6 Figure 3 Figure 1I7 Figure 4 Figure 8

Claims (5)

[Claims] (1) A semiconductor substrate of a first conductivity type, a light-receiving region of a second conductivity type formed on a surface layer of the semiconductor substrate, and a surface layer of the semiconductor substrate surrounding the light-receiving region and not overlapping with the light-receiving region. and a guard ring area formed to
A semiconductor light-receiving device characterized in that the light-receiving region and the guard ring region are respectively connected to different electrodes. (2) 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 multilayer film laminated on the semiconductor substrate, and a surface layer of the semiconductor multilayer film; The light-receiving region of the second conductivity type is formed, and a guard ring region is formed on the surface layer of the semiconductor multilayer film to surround the light-receiving region and not overlap with the region, and the light-receiving region and the guard ring are provided. A semiconductor light-receiving device characterized in that the regions are connected to different electrodes so that voltages are applied independently to each region. (3) 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 multilayer layer formed on the semiconductor substrate; and a semiconductor multilayer film of a first conductivity type formed on the semiconductor multilayer film; a semiconductor film of a second conductivity type, and a high resistance region or a first high resistance region formed in a ring shape on this semiconductor film and electrically separating an inner light receiving region and an outer guard ring region.
What is claimed is: 1. A semiconductor light-receiving device, comprising: a conductivity type region, and the light-receiving region and the guard ring region are respectively connected to different electrodes. (4) Selectively introducing impurities of the second conductivity type into the surface layer of the semiconductor substrate of the first conductivity type, and simultaneously forming a light-receiving region of the second conductivity type and a guard ring region of the second conductivity type surrounding the light-receiving region. and connecting different electrodes to the light receiving region and the guard ring region, respectively. (5) At least an n-type light absorption layer on the n-type semiconductor substrate;
A step of sequentially growing a type avalanche multiplication layer and a p-type semiconductor layer of the same type as the multiplication layer, and forming H, D, H between the region of the p-type semiconductor layer that will become the light receiving part and the region that will become the guard ring part.
a step of ion-implanting at least one of e, Li, Be, Ne, Ar, or n-type impurity to separate a p-type light-receiving region and a p-type guard ring region; A method for manufacturing a semiconductor light receiving device, comprising the step of connecting different electrodes to each of the light receiving region and the p-type guard ring region.