JP2001111095A - Heterojunction bipolar transistor integrated light- receiving circuit and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heterojunction bipolar transistor integrated light-receiving circuit which can supply an integrated light-receiving circuit of single running carrier photodiode, having superior frequency response and saturated output characteristic, while obtaining effective internal quantum efficiency and CR time constant and heterojunction bipolar transistor having superior reliability, high-frequency characteristic, yield, uniformity of the layer, reproducibility and reliability and also can be adapted to an ultra high-speed optical communication photoreceiver and a method of manufacturing the same light-receiving circuit. SOLUTION: In this light-receiving circuit and method of manufacturing the same, since the p-type light-absorbing layer of a single running carrier photodiode is formed in the undoped InGaAs layer corresponding to the collector of the heterojunction bipolar transistor, Be is doped into the p-type light- absorbing layer with the Be ion injection method having superior controllability of the doping profile in the depth direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended to be applied particularly to an ultra-high-speed optical communication photo-receiver. The present invention relates to a photodiode having excellent frequency response and saturation output characteristics while securing effective internal quantum efficiency and CR time constant. Reliability, high frequency characteristics,
The present invention relates to an integrated light receiving circuit with a heterojunction bipolar transistor (HBT) excellent in yield, in-plane uniformity, reproducibility, and reliability, and a method of manufacturing the same.

[0002]

2. Description of the Related Art An HBT uses a semiconductor material having a band gap larger than that of a base for an emitter, so that a high current gain can be obtained without lowering the emitter injection efficiency even if the impurity concentration of a base layer is increased. For this reason, the transistor has many features that are advantageous for improving the performance of the transistor, such as a low base resistance. In particular, III-V
The use of group-compound semiconductors provides excellent electron transport properties,
The selection of materials increases advantages such as expansion of combinations of heterostructures and the possibility of fusion with not only electronic devices but also optical devices. Further, in this, GaAs
The InP / InGaAs heterostructure lattice-matched to a semi-insulating InP substrate having higher thermal conductivity makes it easy to expose the InGaAs base layer by selective wet etching. The surface recombination current of the InGaAs base layer is GaAs.
s is smaller than s, so that it is possible to easily realize a fine dimension element having a small size effect and a high current gain, has a low turn-on voltage, has a high electron mobility of InGaAs, and has other excellent features. It has high potential as an integrated circuit for ultra-high speed and low power consumption, such as excellent internal uniformity and high transconductance (gm).

The collector layer structure of these InP / InGaAs HBTs is undoped InGaAs, or undoped InGaAs, n-type InP and n-type InGaAs.
Since the base layer (high-concentration p-type InGaAs), the collector layer, and the collector contact layer (high-concentration p-type InP) in the HBT structure are composed of quaternary mixed crystals of P,
A long-wavelength band (1.5 μm band) broadband double heterostructure pin photodiode using GaAs as a light absorbing layer can be formed, and an integrated photodetector circuit is manufactured using the same epi-crystal substrate for the HBT and the pin photodiode. It becomes possible to do. However, the optimum layer structure is different between the collector layer structure of the HBT and the pin photodiode absorption layer. If the layer structure is suitable for increasing the speed of the HBT, the absorption layer becomes thinner in the conventional pin photodiode and the CR time constant (C Is the junction capacitance of the diode, and R is the element parasitic resistance +
The line characteristic impedance) increases.

Recently, a uni-traveling-carrier having improved frequency response characteristics and saturation output characteristics of a conventional pin photodiode has been developed.
photodiode) photodiode (UTC-P)
D) has been proposed [Japanese Patent Application Laid-Open No. 9-275224; Ishibashi et al. , OSA
TOPS on Ultrafast Electro
nics and Optoelectronics,
1997]. The feature of the UTC-PD is that the conventional pin
In the photodiode, the light absorbing layer and the carrier traveling layer use the same depleted semiconductor layer (InGaAs), but have a structure capable of separating generation and traveling of carriers. As a result, only carriers (electrons) having a high traveling speed can be used, so that a photodiode having a high response speed and excellent output amplitude characteristics can be realized. According to a conceptual diagram (band diagram) of the UTC-PD [Japanese Patent Application Laid-Open No. 9-275224], the UTC-PD has an n-type electrode layer, a carrier transit layer, and a p-type It is composed of a carrier light absorption layer and a p-type carrier block layer. The light absorption layer has a doping concentration of a certain level or more (2.5 × 10 ¹⁷ to 2.5 × 10 ¹⁸ c) so as not to be depleted in a bias state.
m ^-3 ), and the InP carrier transit layer is set to a low doping concentration so as to be depleted. FIG. 3 shows InP / InG reported by Ericsson et al.
1A shows an epilayer structure of UTC-PD matched to an AsAs HBT structure [U. Eriksson, et al. , El
electronics Letters. 12 ^th Nov
member 1998 Vol. 34, no. 23, p
p. 2270-2271].

A problem when integrating the HBT layer structure with the UTC-PD structure is that the p-type In in the HBT structure is problematic.
GaAs base layer thickness (doping concentration 4 × 10 ¹⁹ cm ^-3
Is about 40 nm, which means that the layer thickness is small to function as a light absorbing layer. The thickness of the base layer depends on the current gain or the current gain cutoff frequency f _T which is a characteristic of the HBT element. In order to increase the thickness, it is essential to reduce the thickness to about 50 nm. On the other hand, the absorption layer thickness of the pin photodiode is determined by the trade-off between the carrier transit time, the CR time constant, and the internal quantum efficiency, but is required to be 200 nm or more. For this reason, a method has been proposed in which a p-type light absorbing layer is formed by introducing a p-type impurity from the outside into a relatively thick undoped InGaAs constituting a part of the collector layer of the HBT [supra, U.S. Pat. Eriksson, et al. , Ele
tronics Letters. 12 ^th Nove
mber 1998 Vol. 34, no. 23, p
p. 2270-2271]. In this case, the introduction of the p-type impurity from the outside is limited to only the plane region corresponding to the UTC-PD, and the plane region corresponding to the HBT element must be masked. U.S. Use a zinc diffusion method having a large diffusion coefficient as a p-type impurity introduced from the outside during the process to form undoped In in the collector layer.
A part of GaAs is converted to a p-type conductive layer. However, when introducing the p-type impurity into the InGaAs layer by using the zinc diffusion method, the problem is that the concentration of the zinc diffusion doping is higher than the level required for the UTC-PD, and furthermore, the profile in the depth direction of the profile is increased. It is poor in controllability.
Further, it is necessary to use a silicon oxide film (SiO ₂ ) or a silicon nitride film (SiN) formed by plasma CVD or sputtering as a zinc diffusion mask.
A major problem is that the inorganic insulating film that induces damage during the film formation may degrade the HBT element portion, particularly the emitter / base junction characteristics.

[0006]

SUMMARY OF THE INVENTION Using the same epi-crystal, InP /
A single traveling carrier photodiode (UTC) with an InGaAs HBT and a high response speed and excellent output saturation characteristics
-PD) in the process of integrating UTC-P
When the light absorption layer of D is formed in the InGaAs layer, HB
In the T layer structure, undoped I corresponding to a part of the collector layer
It is necessary to convert the nGaAs layer into a p-type InGaAs layer by introducing a p-type impurity from the outside. In the conventional example, a measure has been proposed in which a p-type impurity is introduced into an undoped InGaAs layer corresponding to a part of a collector by using a zinc diffusion method. However, in order to perform the zinc diffusion method only on the photodiode region, a silicon oxide film (SiO ₂ ) or a silicon nitride film (SiN) deposited by plasma CVD or sputtering is used as a diffusion mask. If these inorganic insulating films are deposited on the InP / InGaAs emitter / base junction not yet protected by the passivation film, stress or damage to the semiconductor interface at the time of film deposition will cause
There is a risk that the junction characteristics, that is, the transistor characteristics will be degraded. In addition, when a p-type impurity is generally introduced by a zinc diffusion method, the doping profile in the depth direction is poor in controllability. This hinders designing an optimal p-type InGaAs absorption layer in the UTC-PD.

The present invention has been made in view of the above-mentioned circumstances, and provides a UTC-PD having excellent frequency response and saturated output characteristics while securing effective internal quantum efficiency and CR time constant, and reliability, high-frequency characteristics, and the like. A heterojunction bipolar transistor integrated photodetector that can supply an integrated photodetector circuit with an HBT that is excellent in yield, in-plane uniformity, reproducibility, and reliability and can be applied to an ultra-high-speed optical communication photoreceiver It is an object to provide a circuit and a method for manufacturing the circuit.

[0008]

In order to achieve the above object, the present invention provides an n-type InP collector contact layer, an n-type InGaAsP, an undoped InP on a semi-insulating InP substrate.
GaAs collector layer, p-type carbon-doped InGa
Base layer composed of As and p-type carbon doped InGaAsP, n-type InP emitter layer, n-type InP and n-type InGa
A mesa-type heterojunction bipolar transistor composed of an emitter contact layer made of As, the collector contact layer, a carrier transit layer corresponding to a part of the collector layer, a part of the collector layer, and a part of the base layer An integrated light receiving circuit including a light absorbing layer corresponding to (a) and a photodiode composed of a carrier block layer corresponding to a part of the base layer, wherein the light absorbing layer is doped with Be. is there.

Further, the present invention provides a method for forming n
InP collector contact layer, n-type InGaAsP,
Collector layer made of undoped InGaAs, p-type carbon doped InGaAs and p-type carbon doped InGaAsP
Base layer, n-type InP emitter layer, n-type InP
A mesa-type heterojunction bipolar transistor composed of an N-type InGaAs emitter contact layer, the collector contact layer, a carrier transit layer corresponding to a part of the collector layer, a part of the collector layer and the base layer In a method for manufacturing an integrated light receiving circuit including a light absorption layer corresponding to a part of the photodiode and a photodiode constituted by a carrier block layer corresponding to a part of the base layer, only in a plane region forming the photodiode , Carbon-doped InGaAs and carbon-doped InGaAs corresponding to a base layer in a heterojunction bipolar transistor
P, by ion-implanting an acceptor impurity into undoped InGaAs corresponding to a part of the collector layer in the heterojunction bipolar transistor, at least the undoped InGaAs has a carrier concentration of 2.5 × 1
0 ¹⁷ to 2.5 × 10 ¹⁸ cm ^-3 p-type InGa
A step of changing to an As layer, and the acceptor impurity is Be
Wherein the activation anneal performed after the Be ion implantation is performed simultaneously with the dehydrogenation anneal performed for carrier recovery of the base layer composed of carbon-doped InGaAs and carbon-doped InGaAsP in the heterojunction bipolar transistor. It is characterized by having.

[0010] The p-type InGaAs light absorbing layer of the UTC-PD is replaced with undoped InGaAs corresponding to a part of the HBT collector.
In order to form the GaAs layer in the GaAs layer, ion implantation with excellent controllability of the doping profile in the depth direction is used. In particular, an ion implantation method using beryllium (Be), in which implanted ions are almost completely activated even at a low annealing temperature of about 500 ° C. and become carriers (holes), is optimal for introducing a p-type impurity into the InGaAs layer. It is. By injecting Be with multi-stage energy, the concentration can be set to 2.5 × 10 ¹⁷ to 2.5 × 10 ¹⁸ cm ⁻³ required for UTC-PD. In addition, when the ion implantation method is used, a resist can be used as a mask covering the HBT element portion, and there is an advantage that the transistor characteristics do not deteriorate.

In addition, the annealing temperature for activating the ion-implanted Be ions is determined by the carbon-doped InG.
Since the temperature is close to the dehydrogenation annealing temperature of the aAs base layer, it can be shared with the MOCVD grown InP / InGaAs HBT process.

According to the present invention, the effective internal quantum efficiency and CR
Supply integrated photodiodes with photodiodes that have excellent frequency response and saturation output characteristics while ensuring time constants, and HBTs that are excellent in reliability, high-frequency characteristics, yield, in-plane uniformity, reproducibility, and reliability It can be applied to an ultra high-speed optical communication photo receiver.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a mesa-type heterojunction bipolar transistor (InP / InGaAs) fabricated on the same substrate (semi-insulating InP substrate) according to an embodiment of the present invention.
HBT) and Uni-Traveling Carrier Photodiode (UT)
2 shows a schematic cross-sectional structure diagram of (C-PD).

That is, on the semi-insulating InP substrate 11, In
An integrated light receiving circuit including the P / InGaAs HBT and the UTC-PD is formed. The InP / InGaAs H
In the BT, n-type InP is laminated on a semi-insulating InP substrate 11, and n-type InGaAs is formed on the collector contact layer 9.
a collector layer 8 of sP, undoped InGaAs,
7 and the collector electrode 10 are laminated, and the collector layer 7
Base layers 6 and 5 made of p-type carbon-doped InGaAs and p-type carbon-doped InGaAsP are stacked on the base layer. An n-type InP emitter layer 3 and a base electrode 4 are stacked on the base layer 5. An emitter contact layer 2 made of n-type InP and n-type InGaAs is stacked thereon, and an emitter electrode 1 is stacked on the emitter contact layer 2. The UTC-PD
Are formed on the semi-insulating InP substrate 11, the collector contact layer 9, a carrier transit layer 8 'corresponding to a part of the collector layers 8, 7, a part of the collector layers 8, 7 and the base layer 6, 5, a P-type light-absorbing layer 12 and a P-type light-absorbing layer 6 'which correspond to a part of the base layer 5, a P-type carrier blocking layer 5' which corresponds to a part of the base layers 6, 5,
It comprises an n-type electrode layer 9 'corresponding to the collector contact layer 9, an anode electrode 4' and a cathode electrode 10 '.

Next, UTC-PD and InP according to the present invention
A method for manufacturing an integrated photodetector circuit of / InGaAsHBT will be described.

In this embodiment, the Fe-doped semi-insulating I
An n-type InP collector contact layer for forming ohmic resistance on the collector, a collector layer composed of n-type InGaAsP and undoped InGaAs, and a p-type doped with a high-concentration carbon acceptor impurity on the nP substrate by reduced pressure MOVPE (MOCVD). In InGaAs and UTC-PD, a base layer composed of p-type InGaAsP acting as a p-type carrier blocking layer, an n-type InP emitter layer, and an emitter contact layer composed of n-type InP and n-type InGaAs for forming ohmic resistance in the emitter are provided. It was manufactured using an HBT laminated structure which was sequentially epitaxially grown. The epilayer structure is shown in FIG.

As for the HBT, the emitter region is masked with a resist, and the n-type InGaAs emitter contact layer is formed by selective wet etching with citric acid / hydrogen peroxide solution / water or sulfuric acid / hydrogen peroxide solution / water except for the emitter region. N-type InP emitter contact layer and n-type I by selective wet etching with hydrochloric acid / phosphoric acid
The nP emitter layer is removed and p-type carbon-doped InGaAs
Exposing the P base layer. At this time, for the UTC-PD, an n-type InGaAs layer and an n-type InP
The layer is removed, exposing the p-type carbon doped InGaAsP base layer. The resist mask defining the emitter region is removed with an organic solvent.

Next, the UT including at least the HBT element portion
Be ions are implanted by masking a region other than the C-PD with a resist. Specifically, the acceleration voltage is 25 keV, 50 ke
Three-step Be ion implantation of v, 75 keV is performed. The undoped InGaAs layer corresponding to at least a part of the HBT collector layer is implanted under the condition that the carrier concentration satisfies the range of 2.5 × 10 ¹⁷ to 2.5 × 10 ¹⁸ cm ^-3 , and the desired implantation dose and acceleration voltage are obtained. A Be doping profile is obtained. After removing the resist mask for ion implantation with an organic solvent, p-type carbon-doped InGaAsP and p-type
The dehydrogenation annealing of the carbon-doped InGaAs layer is performed.
By this dehydrogenation annealing, p-type carbon-doped InGaAs
At the same time as the carbon acceptors in the P and p-type carbon doped InGaAs layers are activated and the carrier concentration in the base layer is increased, the Be ions implanted into the InGaAs layer in the collector are activated, and the undoped InGaAs layer also has p-type conductivity. As a result, it functions as a light absorbing layer in UTC-PD.

Thereafter, regarding HBT, Pt / Ti /
A Pt / Au base electrode and a Ti / Pt / Au emitter electrode are formed by a vapor deposition / lift-off method. Further, a resist pattern for defining a base / collector region is formed, and p-type InGaAsP / p-type InG is formed by selective wet etching.
aAs base layer, undoped InGaAs / n-type InG
Each of the aAsP collector layers is removed to expose the n-type InP collector contact layer.
/ Pt / Au collector electrode is formed.

On the other hand, in the case of UTC-PD, an anode electrode corresponding to a base electrode is formed by evaporation and lift-off, and a p-type InGaAsP is formed using the same resist mask as that of the HBT.
Carrier block layer, p-type In implanted with Be ions
The GaAs light absorption layer and the undoped InGaAsP carrier traveling layer are selectively wet-etched to expose the n-type InP electrode layer corresponding to the collector contact layer of the HBT, thereby forming a cathode electrode corresponding to the collector electrode.

[0022]

As described above, according to the present invention, the p-type light absorbing layer of the uni-traveling carrier photodiode (UTC-PD) is made of undoped InG corresponding to an HBT collector.
By using a Be ion implantation method having excellent controllability of the depth direction doping profile to be formed in the aAs layer, the problems of the prior art can be solved, and the effective internal quantum efficiency and CR time constant can be improved. We can supply photodiodes with excellent frequency response and saturation output characteristics while securing HBTs with excellent reliability, high frequency characteristics, yield, in-plane uniformity, reproducibility, and reliability. ,
It can be applied to an ultra-high-speed optical communication photo receiver.

[Brief description of the drawings]

FIG. 1 shows InP / InGaAs H fabricated on the same substrate (semi-insulating InP substrate) according to an embodiment of the present invention.
1 shows a schematic cross-sectional structure of a BT and a UTC-PD.

FIG. 2 shows an InP / InGa according to an embodiment of the present invention.
It is explanatory drawing which shows the epilayer structure of As HBT and UTC-PD.

FIG. 3 is an explanatory diagram showing an epilayer structure of a conventional InP / InGaAs HBT and UTC-PD.

[Explanation of symbols]

Reference Signs List 1 emitter electrode 2 n-type InGaAs / n-type InP emitter contact layer 3 n-type InP emitter layer 4 base electrode 4 'anode electrode 5 p-type carbon-doped InGaAsP base layer 5' p-type carrier block layer 6 p-type carbon-doped InGaAs base layer 6 'p-type light absorption layer 7 undoped InGaAs collector layer 8 n-type InGaAsP collector layer 8' carrier transit layer 9 n-type InP collector contact layer 9 'n-type electrode layer 10 collector electrode 10' cathode electrode 11 semi-insulating InP substrate 12 P-type light absorbing layer (I) formed by Be ion implantation
nGaAs)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01L 29/205 H01L 29/72 21/331 29/73 F term (Reference) 4M118 AA10 AB05 BA02 CA05 CA15 CB01 EA01 FC09 FC16 GA10 5F003 AP05 BA91 BA92 BB02 BB04 BC02 BC04 BE02 BE04 BF06 BH99 BJ12 BM02 BM03 BP01 BP23 BP41 5F049 MA13 MB07 MB11 MB12 NA03 NB01 PA10 PA11 QA09 SS04 5F082 AA40 BA21 BA22 BA35 BA01 BA02 BA50

Claims (2)

[Claims] 1. An n-type InP collector contact layer, an n-type InGaAsP, and an undoped I on a semi-insulating InP substrate.
Collector layer made of nGaAs, p-type carbon-doped InG
base layer composed of aAs and p-type carbon doped InGaAsP, n-type InP emitter layer, n-type InP and n-type InG
a mesa-type heterojunction bipolar transistor composed of an emitter contact layer of aAs; the collector contact layer; a carrier transit layer corresponding to a part of the collector layer; a part of the collector layer and a part of the base layer Wherein the light absorbing layer is Be-doped in an integrated light receiving circuit including a light absorbing layer corresponding to the above, and a photodiode comprising a carrier block layer corresponding to a part of the base layer. Bipolar transistor integrated light receiving circuit. 2. An n-type InP collector on a semi-insulating InP substrate.
Contact layer, n-type InGaAsP, undoped I
Collector layer made of nGaAs, p-type carbon-doped InG
a base comprising aAs and p-type carbon-doped InGaAsP
Layer, n-type InP emitter layer, n-type InP and n-type InG
Mesa composed of emitter contact layer composed of aAs
Type heterojunction bipolar transistor and the collector
Contact layer, carrier corresponding to part of the collector layer
Running layer, equivalent to part of the collector layer and part of the base layer
Light absorbing layer and a carrier layer corresponding to a part of the base layer.
Integration including a photodiode composed of a lock layer
In the method for manufacturing a light receiving circuit, only in a plane region forming the photodiode,
For base layer in heterojunction bipolar transistor
Corresponding carbon-doped InGaAs and carbon-doped InG
aAsP in heterojunction bipolar transistor
Undoped InGaAs corresponding to a part of the collector layer
Ion implantation of acceptor impurities reduces
At least the above undoped InGaAs has a carrier concentration of 2.
5 × 10 ¹⁷From 2.5 × 10¹⁸cm^-3P-type I within the range
a step of changing to an nGaAs layer, and wherein the acceptor impurity is Be;
Activation annealing performed after
-Doped InGaAs and carbon in semiconductor transistors
Carrier times of base layer composed of silicon-doped InGaAsP
Performed simultaneously with dehydrogenation annealing performed for recovery
Heterojunction bipolar process comprising the steps of:
A method for manufacturing a transistor integrated light receiving circuit.