阅读说明：本技术 半导体光集成元件及其制造方法 (Semiconductor optical integrated element and method for manufacturing the same ) 是由 进藤隆彦 藤原直树 佐野公一 石井启之 松崎秀昭 山田贵 堀越建吾 于 2019-02-28 设计创作，主要内容包括：一种半导体光集成元件的制造方法,在半导体光集成元件(AXEL)的进一步高输出化中,不追加检查工序,防止制造成本的增大。所述半导体光集成元件的制造方法由以下步骤构成：DFB激光器、EA调制器以及SOA被单片集成到同一基板上,使光轴方向一致地二维排列多个在光出射方向上按所述DFB激光器、所述EA调制器以及所述SOA的顺序配置的半导体光集成元件,从而形成半导体晶片的步骤；以与光出射方向正交的面劈开所述半导体晶片,形成多个所述半导体光集成元件在与光出射方向正交的方向一维排列并且邻接的所述半导体光集成元件共用同一劈开端面作为光出射面的半导体条的步骤；经由将所述SOA的电极与所述DFB激光器的电极电连接的连接布线部进行通电驱动来检查所述半导体条的所述各半导体光集成元件的步骤；以及在检查后,在与邻接的半导体光集成元件的边界线分离所述半导体条的所述各半导体光集成元件,由此将连接所述SOA的电极与所述DFB激光器的电极的所述连接布线部切断,从而进行电分离的步骤。(A method for manufacturing a semiconductor optical integrated device (AXEL) is provided, which does not need to add an inspection process in order to further increase the output power of the semiconductor optical integrated device, thereby preventing the increase of the manufacturing cost. The manufacturing method of the semiconductor light integrated element comprises the following steps: a step of monolithically integrating the DFB laser, the EA modulator, and the SOA onto the same substrate, and two-dimensionally arranging a plurality of semiconductor optical integrated elements arranged in the light exit direction in the order of the DFB laser, the EA modulator, and the SOA so that the optical axis directions are aligned, thereby forming a semiconductor wafer; cleaving the semiconductor wafer with a surface orthogonal to a light emission direction to form a semiconductor strip in which a plurality of the semiconductor light-integrated devices are one-dimensionally arranged in the direction orthogonal to the light emission direction and the adjacent semiconductor light-integrated devices share the same cleaved end surface as a light emission surface; a step of inspecting the respective semiconductor light integration elements of the semiconductor bar by performing energization driving via a connection wiring section that electrically connects an electrode of the SOA and an electrode of the DFB laser; and after the inspection, separating the semiconductor photonic integrated devices of the semiconductor strip at boundary lines with adjacent semiconductor photonic integrated devices, thereby cutting the connection wiring portion connecting the electrode of the SOA and the electrode of the DFB laser, and electrically separating the semiconductor photonic integrated devices.)

1. A semiconductor optical integrated element in which a DFB laser, an EA modulator, and an SOA are monolithically integrated on the same substrate, the semiconductor optical integrated element being arranged in the order of the DFB laser, the EA modulator, and the SOA in a light exit direction,

forming a plurality of semiconductor light-integrating elements such that optical axis directions are aligned one-dimensionally in a direction orthogonal to a light emission direction and adjacent ones of the semiconductor light-integrating elements share the same cleaved end face as a light emission face,

each of the semiconductor light-integrated elements of the semiconductor strip has a connection wiring portion that electrically connects an electrode of the SOA and an electrode of the DFB laser,

the connection wiring portion is formed across a boundary line with an adjacent semiconductor light-integrated element in the semiconductor stripe.

2. The semiconductor light integrating element as recited in claim 1,

the DFB laser, the EA modulator, and the SOA are formed from a commonly formed mesa strip configuration,

the sidewalls of the mesa stripe structure are formed to have a buried heterostructure buried by a co-grown p-type and n-type semiconductor layer.

3. A semiconductor light integrating element as claimed in claim 1 or 2,

the length of the SOA is formed to be 150 μm or more.

4. A method for manufacturing a semiconductor optical integrated device, comprising the steps of:

a step of monolithically integrating the DFB laser, the EA modulator, and the SOA onto the same substrate, and two-dimensionally arranging a plurality of semiconductor optical integrated elements arranged in the light exit direction in the order of the DFB laser, the EA modulator, and the SOA so that the optical axis directions are aligned, thereby forming a semiconductor wafer;

cleaving the semiconductor wafer with a surface orthogonal to a light emission direction to form a semiconductor strip in which a plurality of the semiconductor light integrated devices are one-dimensionally arranged in the direction orthogonal to the light emission direction and the adjacent semiconductor light integrated devices share the same cleaved end surface as a light emission surface;

inspecting the semiconductor light-integrated elements in a state of the semiconductor strip; and

a step of cutting each semiconductor optical integrated element of the semiconductor bar at a boundary line with an adjacent semiconductor optical integrated element after the inspection, thereby electrically separating the SOA from the DFB laser,

in the step of forming the semiconductor wafer, a connection wiring portion that electrically connects the SOA and the DFB laser across a boundary line with an adjacent semiconductor optical integrated device is formed in each semiconductor optical integrated device.

5. The method for manufacturing a semiconductor light integrated device as recited in claim 4,

in the step of inspecting, the SOA and the DFB laser are simultaneously electrically driven via the connection wiring section to perform inspection.

Technical Field

The present invention relates to a semiconductor optical integrated device such as a modulated laser in which an electric field absorption (EA) optical modulator and a semiconductor laser are integrated on a semiconductor substrate such as InP, and a method for manufacturing the same. More particularly, the present invention relates to a high-output semiconductor optical integrated device including an EA modulator, a Semiconductor Optical Amplifier (SOA), and a Distributed Feedback (DFB) laser, and a method for manufacturing the same.

Background

With the recent spread of video distribution services and the increase in demand for mobile traffic, network traffic has increased explosively, and in particular, in a network area called an access system, discussion about next generation networks has been activated. As these next-generation access system networks tend to require extension of transmission distance and multi-branching, semiconductor modulated light sources used therein are also required to increase the output of light in order to compensate for the increase in the branching ratio.

An electric field absorption modulator integrated dfb (eadfb) laser has a higher extinction characteristic and an excellent chirp (chirp) characteristic than a direct modulation laser that directly drives laser light by modulating an electric signal, and thus has been used in a wide range of applications including a light source for an access system network.

Fig. 1 shows a schematic substrate cross-sectional view along the light emission direction of a conventional general EADFB laser. A typical EADFB laser has a waveguide configuration in which a DFB laser 11 and an EA modulator (EAM)12 are monolithically integrated in a light exit direction within the same chip. The DFB laser 11 has an active layer 11a including a Multiple Quantum Well (MQW), and oscillates at a single wavelength by a diffraction grating 11b formed in a resonator. The EA modulator 12 has a light absorption layer 12a including a Multiple Quantum Well (MQW) having a different composition from the DFB laser, and modulates laser light by changing the light absorption amount by voltage control. The EA modulator 12 is electrically driven with a modulation signal to dim light under the condition of transmitting/absorbing the output laser light from the DFB laser 11, thereby converting the electric signal into an optical signal (optical modulation) and emitting it.

The EADFB laser has a problem that since light absorption in the EA modulator is used for optical modulation, sufficient extinction characteristics and high light output are in a trade-off relationship in principle.

Fig. 2 shows the extinction curve of a typical EADFB laser, illustrating the principle of light intensity modulation. One method for achieving high output in a general EADFB laser is to reduce the absolute value of a reverse bias applied to the EA modulator and to suppress light absorption in the EA modulator. However, in this case, since the EA modulator operates in a portion where the steepness of the extinction curve is lowered, the Dynamic Extinction Ratio (DER) which is the modulation characteristic deteriorates.

Another method is to increase the drive current of the DFB laser to increase the intensity of laser light incident on the EA modulator from the DFB laser. However, in this method, not only the power consumption of the DFB laser increases, but also the light absorption in the EA modulator and the photocurrent associated with the light absorption also increase, and the extinction characteristic deteriorates, so that the power consumption of the entire chip excessively increases. As described above, it is difficult to achieve both sufficient optical output and modulation characteristics (dynamic extinction ratio) in the conventional EADFB laser, and an excessive increase in power consumption cannot be avoided.

In order to solve this problem, conventionally, an EADFB Laser (SOA amplified read EADFB Laser: AXEL) has been proposed in which a Semiconductor Optical Amplifier (SOA) is further integrated at the light emitting end of the EADFB Laser (non-patent document 1).

Fig. 3 is a schematic substrate cross-sectional view of an EADFB laser (AXEL) integrated with a conventional SOA. In the AXEL, laser signal light generated by the DFB laser 31 and modulated by the EA modulator 32 is independently amplified and output through the monolithically integrated SOA region 33. Therefore, in the AXEL, the optical output can be increased without deteriorating the quality of the optical signal waveform. In addition, in the AXEL, the drive current of the DFB laser 31 and the photocurrent of the EA modulator 32 can be increased without excessively increasing the output as compared with the conventional EADFB laser.

In the AXEL, the same MQW structure as that of the active layer 31a of the DFB laser 31 is used for the active layer 33a of the SOA 33. Therefore, a device can be manufactured in the same manufacturing process as that of the conventional EADFB laser without adding a regrowth process for integrating the SOA region.

In addition, as a feature of the AXEL, as shown in fig. 3, the SOA33 in the same element may be electrically connected to the DFB laser 31 and driven by the same terminal. By driving the SOA33 and the DFB laser 31 from the same terminal, a part of the drive current of the DFB laser 31 is supplied to the SOA 33. The current distribution is determined by the ratio (volume) of the length of the DFB laser 31 to the length of the SOA33, so that the respective regions of the SOA33 and the DFB laser 31 will operate at the same current density. By this driving method, the AXEL can be operated by the same driving method without increasing the number of terminals as compared with the conventional EADFB laser (patent document 1).

Fig. 4 is a schematic view of a chip showing the arrangement of electrodes in each region of a conventional AXEL. In fig. 4, a part of the substrate of the chip is cut out to show the sectional structure of each region for easy understanding. In the conventional AXEL shown in fig. 4, an electrode pattern in which the electrodes (41c, 43c) of the SOA region 43 and the DFB laser region 41 are connected is provided in the device at the chip fabrication stage, and the SOA and the DFB laser can be driven from a common terminal in the inspection step after the chip fabrication. Thus, in the AXEL, the inspection process can be performed without increasing the number of steps associated with the integration of the SOA region, and the normality of each region can be determined by performing the same inspection process as that of the conventional EADFB laser.

As described above, the AXEL has a significant advantage over the conventional EADFB laser in that it can be manufactured in the same manufacturing process and inspection process as the EADFB laser, in addition to high output and low power consumption by integrating the SOA region.

Disclosure of Invention

Problems to be solved by the invention

However, in recent years, particularly in an access system network or the like, there has been an increasing demand for higher output of modulated light sources as the branching ratio of a Splitter (Splitter) increases. As described above, the AXEL is superior to a general EADFB laser in low power consumption and high output characteristics, but further high output is indispensable for achieving a light output required in the future.

Further, as another method of increasing the light output of the AXEL, it is possible to increase the optical gain obtained in the SOA region. As described above, in the conventional AXEL, since S drives the OA and DFB lasers through a common terminal and operates the OA and DFB lasers, when the drive current for stably operating the DFB laser is adjusted, the amount of current applied to the SOA is also determined by the volume ratio of the OA and DFB lasers.

Here, in order to operate the AXEL with a higher output, it is necessary to independently drive the SOA and the DFB laser by different current sources and supply a sufficient drive current to the SOA. In addition, for increasing the output of the AXEL, it is desirable to design the SOA length to be long. This is because, as described above, if the resonator length of the DFB laser is increased to increase the optical output from the DFB laser, the photocurrent and the power consumption of the EA modulator increase.

Therefore, in order to increase the output, it is necessary to design the SOA length to be large so that the optical amplification can be performed independently without being affected by the optical absorption in the EA modulator. However, a problem that may occur when a long SOA length is used is that waveform quality deteriorates due to a Pattern effect (Pattern effect) accompanying carrier wave motion inside the SOA.

In order to suppress the pattern effect inside the SOA, it is necessary to sufficiently increase the carrier density inside the SOA, in which case the DFB laser and the SOA also need to be driven independently, and the current density of the SOA is set high relative to the DFB laser.

From the above, it is essential to make the SOA and the DFB laser independently drivable for further increasing the output of the AXEL. In this case, an inspection step for separately confirming the normality of the SOA region needs to be added at the time of manufacturing the AXEL, and this inspection step causes a problem that the manufacturing cost increases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor optical integrated device (AXEL) and a method for manufacturing the same, which can achieve further higher output, and which can prevent an increase in manufacturing cost without requiring an additional inspection step for separately confirming normality of an SOA region in manufacturing the AXEL.

Means for solving the problems

To achieve the above object, the present invention is characterized by having the following configuration.

(constitution of the invention 1)

A semiconductor optical integrated device in which a DFB laser, an EA modulator, and an SOA are monolithically integrated on the same substrate, wherein the semiconductor optical integrated device is arranged in the order of the DFB laser, the EA modulator, and the SOA in a light emission direction, wherein a plurality of semiconductor optical integrated devices are formed such that the optical axes of the semiconductor optical integrated devices are aligned one-dimensionally in a direction orthogonal to the light emission direction, and the adjacent semiconductor optical integrated devices share the same cleaved end face as a light emission face, wherein each of the semiconductor optical integrated devices in the semiconductor strip has a connection wiring portion for electrically connecting an electrode of the SOA and an electrode of the DFB laser, and the connection wiring portion is formed across a boundary line between the semiconductor strip and the adjacent semiconductor optical integrated device.

(constitution of the invention 2)

The semiconductor optical integrated device according to configuration 1 of the present invention is characterized in that the DFB laser, the EA modulator, and the SOA are formed of a mesa stripe structure formed collectively, and sidewalls of the mesa stripe structure are formed to have a buried heterostructure buried in p-type and n-type semiconductor layers grown collectively.

(constitution of the invention 3)

The semiconductor optical integrated device according to configuration 1 or 2 of the invention is characterized in that the SOA is formed to have a length of 150 μm or more.

(constitution of the invention 4)

A method for manufacturing a semiconductor optical integrated device, comprising the steps of: a step of monolithically integrating the DFB laser, the EA modulator, and the SOA onto the same substrate, and two-dimensionally arranging a plurality of semiconductor optical integrated elements arranged in the light exit direction in the order of the DFB laser, the EA modulator, and the SOA so that the optical axis directions are aligned, thereby forming a semiconductor wafer; cleaving the semiconductor wafer with a surface orthogonal to a light emission direction to form a semiconductor strip in which a plurality of the semiconductor light integrated devices are one-dimensionally arranged in the direction orthogonal to the light emission direction and the adjacent semiconductor light integrated devices share the same cleaved end surface as a light emission surface; inspecting the semiconductor light-integrated elements in a state of the semiconductor strip; and a step of electrically separating the SOA from the DFB laser by cutting each semiconductor optical integrated element of the semiconductor strip at a boundary line between the semiconductor optical integrated element and an adjacent semiconductor optical integrated element after the inspection, wherein in the step of forming the semiconductor wafer, a connection wiring portion for electrically connecting the SOA and the DFB laser across the boundary line between the semiconductor optical integrated element and the adjacent semiconductor optical integrated element is formed in each semiconductor optical integrated element.

(constitution of the invention 5)

In the method of manufacturing a semiconductor optical integrated device according to configuration 4 of the present invention, in the step of inspecting, the SOA and the DFB laser are simultaneously energized and driven via the connection wiring portion to perform the inspection.

Effects of the invention

As described above, according to the semiconductor optical integrated device and the method for manufacturing the same of the present invention, it is possible to prevent an increase in manufacturing cost without adding an inspection step when further increasing the output of the semiconductor optical integrated device such as AXEL.

Drawings

Fig. 1 is a schematic substrate cross-sectional view of a conventional general EADFB laser.

Fig. 2 is a diagram illustrating the principle of the extinction curve and intensity modulation of a conventional general EADFB laser.

Fig. 3 is a schematic cross-sectional substrate view of an EADFB laser (AXEL) integrated with a conventional SOA.

Fig. 4 is a chip perspective view showing the arrangement of electrodes in each area of a conventional AXEL.

Fig. 5 (a) is a top view of an AXEL chip in example 1 of the present invention, and fig. 5 (b) is a view showing a state in the middle of a manufacturing process in which a plurality of chips on a semiconductor wafer are two-dimensionally arranged.

Fig. 6 is a plan view showing a part of a semiconductor strip in the AXEL inspection process in example 1 of the present invention.

Fig. 7 is a cross-sectional view of a waveguide of an AXEL chip in embodiment 2 of the present invention.

Fig. 8 is a plan view showing a part of a semiconductor strip in an AXEL inspection process in example 2 of the present invention.

Detailed Description

(outline of the invention)

In order to solve the above-described problems, the present invention provides a connection wiring portion for electrically connecting an SOA and a DFB laser in an AXEL chip (element) as an electrode pattern in the manufacture of the chip, and the connection wiring portion is arranged so as to straddle the region of adjacent chips. In this case, the connection wiring portion is arranged to be cut in a step of separating the adjacent chips after the inspection. Since the inspection step for checking the normality of each region at the time of manufacturing is performed in a state of a semiconductor bar including a plurality of chips arranged one-dimensionally in a direction orthogonal to the optical waveguide direction, the SOA of each chip (element) and the DFB laser are electrically connected, and both can be inspected and checked at the same time.

When the adjacent elements are separated into individual chips after the inspection process, the connection wiring portions are cut, and the SOA and the DFB laser in each chip element are electrically separated and can be driven independently.

In the present invention, in the AXEL which independently drives the SOA of the AXEL and the DFB laser, the cost increase in the manufacturing and inspection processes is suppressed, and a modulated light source with ultra-high output is realized at the same manufacturing process and manufacturing cost as those of the conventional EADFB laser. That is, in the inspection step, the SOA section of each element in the semiconductor strip is electrically connected to the EADFB laser section, and the normality of the SOA and the DFB laser can be inspected at the same time by applying a current to one electrode on the same element as that of the conventional EADFB laser. Further, by separating the semiconductor strip into individual elements after the inspection process, the SOA and the DFB laser in each element can be electrically separated, and the SOA and the DFB laser can be operated independently at an arbitrary current value at the time of actual driving.

The above-described effect of the present invention is not directly related to the ratio of the SOA length of the AXEL to the DFB laser length, and the respective lengths, but when the SOA length is designed to be long for increasing the output of the AXEL, it is necessary to supply a sufficient drive current to the SOA in order to suppress the code pattern effect. Therefore, in the case where an SOA that is relatively long with respect to the DFB laser is employed, it is or is not indispensable to independently drive the SOA and the DFB laser. In the AXEL using 300 μm, which is a length of a general DFB laser, when a conventional SOA and DFB laser are operated by common driving, the influence of the pattern effect becomes remarkable when the SOA length is 150 μm or more. Therefore, the present invention is particularly effective in an AXEL having an SOA length of 150 μm or more.

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