JPS59181082A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the positioning accuracy of a reflecting surface by mesa etching the side face of a mount of a semiconductor, forming the opposite surface of a high melting point barrier electrode layer in the same surfce as the reflecting surface of a resonator, and forming the peripheral edge of the heat sink electrode layer inside the high melting point barrier electrode layer. CONSTITUTION:A contacting electrode layer 6 and a high melting point barrier electrode layer 7' are formed on a semiconductor wafer of InGaAsP/InP, a striped window perpendicularly crossing the layer 7' is formed. Au is selectively plated by a mask for covering completely the striped window, and a rectangular heat sink Au electrode layer 2 is formed. After an ohmic electrode 8 is formed on the back surface of the wafer, the layer 6 is etched through the window in the same shape as the layer 7', with the layer 7' as a mask InGaAsP and InP are selectively etched to form a slot 14. An element is isolated along the slot 14, and the layer 2 is mounted on the heat sink with the layer 2 underneath.

Description

[Detailed description of the invention] The present invention relates to a semiconductor laser and a method for manufacturing the same.

Semiconductor lasers used as light sources for optical fiber communications and information processing are used at high current densities, so it is important to use highly reliable electrodes and to dissipate heat effectively.

Conventionally, Ti has been used as a highly reliable electrode with a large heat dissipation effect on the semiconductor surface of the active layer near the p-n junction.
/Pt/Au electrodes are often used. The Au electrode layer of this Ti/Pt/Au electrode often serves as a heat sink and is a thick layer of 10 to 20 μm. Since the thick Au tit pole layer is difficult to separate by opening the valve when forming the reflective surface of the resonator, conventionally, selective etching or selective plating has been used to
Only the U electrode layer was separated into rectangular electrodes, and the valve was opened at the center of a striped groove portion with a width of 20 to 30 μm where there was no Au electrode layer.

However, with this electrode structure, even if an attempt is made to open the center of a striped groove where there is no Au electrode layer, the valve opening edge does not run straight, but is often bent and biased toward one laser element side. Therefore, in the electrode layer on the active region near the reflective surface, Au
In the laser element on the side where the area without the electrode layer is increased, the dissipation of heat generated near the reflective surface becomes worse. Also, the valve opening is made of Au.
In the laser element on the side along the end face of the electrode layer, S
n.

When a laser element is mounted in a so-called upside-down type on a heat sink such as diamond or Sl using a fusing material such as Au+8R, the fusing material that crawls up the side surface of the Au electrode is attached to the side surface of the Pt or Ti electrode. This has the disadvantage of accelerating the deterioration of the characteristics of the element, which does not come into contact with the semiconductor beyond this point. In addition, the leakage current of the p-n junction increases when the exposed p-n junction on the side surface of the device is scratched with a razor blade when separating the device in a direction perpendicular to the valve opening plane, or with tweezers that grip the laser device. Deterioration was observed.

Figure 1 is a schematic diagram showing a conventional InGaAsP/InP-based planar stripe structure semiconductor laser equipped with an Au electrode layer for a heat sink and its manufacturing method. A top view of the wafer in FIG.
FIG. 4(c) is a sketch of the laser element after being separated from the wafer 1 shown in FIGS. This figure (a) and layer 13
This shows that a stripe-shaped active region formed by selective Zn diffusion is located from 1 to 12 to the p-type InP cladding layer 12. Furthermore, the axis of the laser resonator is located directly below this dashed line 1. An n-type InP cladding layer 1 is sequentially formed on an n-deaf InP substrate 9.
05 InG with a composition corresponding to the oscillation wavelength of 1.3 μm
aAsP active layer 11° p-type InP cladding layer 12. A p-type InGaAsP cap layer 13 in which Zn is selectively diffused in stripes is formed along the dashed line, and T
A contact electrode layer 6 which is a Schottky-type ohmic electrode made of i, a high melting point barrier electrode layer 7 made of Pt, and a heat sink A with a thickness of 10 to 20 μm with electrodes separated into rectangular shapes.
A u electrode layer 2 is formed, and an n Iq ohmic electrode layer 8 of AuGeNi is formed on the back surface of the n-type InP substrate 9.

Conventionally, when opening the center of the stripe groove 3 between the heat sink Au electrode layers 2 separated into rectangular shapes from the above-mentioned wafer state, the opening edge of the valve is bent as shown by the broken line 4-4',
A valve opening surface was sometimes formed along the end face of the UTI pole layer 2, resulting in many laser elements having poor symmetry and varying shapes. The width of the stripe groove 3 is wide enough to accommodate a valve opening blade, and is usually 20 to 30 microns. Therefore, as mentioned above, if the opening plane deviates from the center of the stripe groove 3, the laser element on one side will be 2 degrees from the position of the cavity reflecting surface.
A portion where the Au electrode layer 2 for a heat sink was not formed was formed over a range of 0 to 30 μm, which resulted in poor dissipation of heat generated near the resonator reflective surface 9 and induced deterioration of the reflective surface.

In addition, on the side where the valve opening surface coincides with the end surface of the Au electrode layer 2,
When mounting the Au electrode 2 for the heat sink of the laser element on the heat sink side of Si or diamond using a fusing material such as Sr or AuSn, the fusing material is 71u,
This has the disadvantage that it tends to come into contact with the semiconductor 5 through the side surfaces of the Pt and Ti electrode layers, accelerating the deterioration of the laser device characteristics. In addition, when the device is separated in the direction perpendicular to the valve opening plane, the exposed p-n junction on the side of the device may be scratched with a razor blade or tweezers used to scrap the laser device, causing an increase in the leakage current of the p-n junction. Deterioration of characteristics was observed.

An object of the invention is to provide a semiconductor laser and a method for manufacturing the same, in which a resonator reflecting surface can be formed with good position control by opening a valve, and the manufacturing yield is high.

The structure of the semiconductor laser according to the present invention is as follows:
In a semiconductor laser in which an ohmic electrode layer including a U electrode layer and a high melting point barrier electrode layer formed under an Au electrode layer is carved on the surface of the semiconductor mount side, the reflective surface of the resonator The side surface of the semiconductor on the mount side except for the vicinity thereof is mesa-etched; the end face of the high melting point barrier electrode layer in the axial direction of the resonator is substantially in the same plane as the reflective surface; Au for heat sink
It is assumed that the periphery of the electrode layer is located inside the periphery of the high melting point barrier electrode layer.

The structure of the method for manufacturing a semiconductor laser according to the present invention includes a first step of sequentially forming a contact electrode layer and a high melting point barrier electrode on the mount side surface of a semiconductor wafer; A first striped window located at the axial length of the resonator and a second striped window that is repeated at a pitch of 9 and intersects at right angles to the first striped window and is interrupted only above the resonator axis. a second step of providing a striped window in the high melting point barrier electrode layer, completely covering the first and second striped windows and also forming a narrow width striped window in the second striped window; Selective plating of Au was performed using a grid-like photoresist mask covered with connected stripes as a plating mask to form a pseudo-rectangular A.
u. A third step of forming an electrode layer, etching the contact electrode layer into the same shape as the high melting point barrier layer through the first and second striped windows, and further etching the semiconductor using the high melting point barrier layer as a mask. a fourth step of performing deep mesa etching; a fifth step of forming a reflective surface of the resonator by forming folds along the grooves formed by mesa etching through the second striped window; and a fifth step of forming a reflective surface of the resonator. The method is characterized by comprising a sixth step of separating the elements along the grooves formed by mesa etching through the shaped windows.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram for explaining an embodiment of a semiconductor laser and its manufacturing method according to the present invention. FIG. 2(a) is a top view of a wafer before element separation by opening a valve, and FIG. The same figure (a
) is a sectional view taken along the two-dot chain line A-A', the same figure (C)
2 is a sketch of the laser structure after element separation from Ueno shown in FIG. The layer structure of the semiconductor 5 is the same as that in FIG. 1, and in FIG. 2(c), the p-n junction surface 1 attached to the active layer is
Only 6 is simplified and shown with a thick line.

First, a contact electrode layer 6 of a Schottky type ohmic electrode made of Ti or Or is formed on a semiconductor wafer similar to that shown in FIG. W
Alternatively, a high melting point barrier electrode layer 7' made of Mo is formed by vacuum deposition or high frequency sputter deposition. Next, the high melting point barrier electrode layer 7' is provided with a first striped window parallel to the resonator axis and located between adjacent resonator axes, and a first striped window that is repeated with the resonator length as a repeating pitch. The second section intersects the window at right angles and is interrupted above the resonator axis.
striped windows and photoresist method and W or MO x7 coating solution 4 HN40ET+II (20
! -7, 1゛← is provided by selective etching. Next, a lattice-like structure was formed, which completely covered the first and second striped windows and also covered the broken portions of the second striped windows by connecting stripes with a narrow width (approximately 5 to 10 μm). Selective plating of Au is performed using a photoresist mask as a plating mask, and a quasi-rectangular Au electrode layer 2 for a heat sink having a protrusion shape on the reflective surface side is formed in the active region 15 near the reflective surface.

Next, polish the back side of the n-type InP substrate to reduce the wafer thickness to approximately 100 mm.
After thinning by 11 mK, an n-type ohmic electrode 8 of AuGeNi is formed. Subsequently, through the first and second striped windows provided in the high melting point barrier electrode layer 7',
A contact electrode layer 6 of Ti or Or is etched in the same shape as the high melting point barrier electrode layer 7', that is, into a lattice window with striped windows interrupted only in the vicinity of the active region, and further using the high melting point barrier layer 7' as a mask. , t) InGaA with an etching solution of sulfuric acid + hydrogen peroxide type or hydrochloric acid/deca hydrogen peroxide type.
Selective etching of sP and InP to depth 20-3074
A groove portion 14 of m is formed in the semiconductor 5. Thereafter, the second stripe-shaped window is passed through the mesa-etched groove to form a reflective surface of the resonator, thereby making it possible to configure the reflective surface in the vicinity of the active region without the groove as a valve open surface. Finally, device isolation is completed along the mesa-etched groove through the first striped window, and the obtained laser device is placed on a heat sink of Si or diamond using a bonding material such as Sn or AuSn. The laser device is mounted with the heat sink Au electrode layer 2 facing down.

According to the manufacturing method of the present invention, the srj! The reflective surface near the active/heel region where Jm runs and has no grooves is composed of a valve-open surface, and the position of the interosseous surface is highly controllable, and as a result, the Au heat sink
Even if the width between the electrode layers is narrowed to 5 to 10 .mu.m, the center of the gap can be formed between the bones, allowing effective heat dissipation in the vicinity of the reflective surface of the active region.

Furthermore, since the distance between the position of the reflective surface and the end face of the Au electrode layer for the heat sink can be kept constant with good controllability, the periphery of the Au electrode layer for the heat sink, including the grooved portion other than the reflective surface, is a high melting point buffer. It is located completely inside the periphery of the electrode layer. Therefore, since the fusing material does not pass through the side surfaces of the high-melting point buffer electrode layer and the contact electrode layer and come into contact with the semiconductor, the device characteristics can be maintained stably. Furthermore, since the side surfaces of the laser element are mesa-etched except for the vicinity of the reflecting surface of the resonator, the pn junction on the side surfaces is recessed inward from the side surface of the n-type InP substrate. Therefore, when narrowing the sides of the laser element other than the reflective surface with a pin set, etc., the pins etc. do not touch the P-11 junction on the side, so do not scratch or stain the P-N junction. This also provides the additional effect of not deteriorating the device characteristics.

In the above embodiment, the same effect can be obtained by replacing Ti in the contact electrode layer with Or and replacing W in the high melting point buffer electrode layer with M6 in the Schottky type ohmic electrode. It is also possible to use Pt as the high melting point buffer electrode layer, but in this case, Pt cannot be easily chemically etched and requires physical etching such as ion etching.

Although the planar stripe structure has been described as an example above, it goes without saying that the method of the present invention can also be applied to a structure in which most of the semiconductor surface is covered with an insulating film, such as the 8102 stripe structure. This insulating film is S
In, besides PSG (phospho-ailica
(te glass) or SiN may also be used. In such a structure, there is no need for a contact electrode layer such as Ti or Or, and if 1 to 2% bromine methanol is used as the mesae or tinda solution, a V-shaped groove can be created and the interosseous area can be realized with more precision. .

Although the explanation has been given above using InGaAs'P/InP and i long wavelength lasers as examples, it goes without saying that the present invention can also be applied to nine conductor lasers using other semiconductor materials.
It's too tall.

As described above, according to the present invention, it is possible to provide a semiconductor laser and a method for manufacturing the same, in which the resonator reflecting surface can be formed between the bones with good controllability, and the manufacturing yield is high.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a conventional semiconductor laser and its manufacturing method, and FIG. 2 is a diagram for explaining an embodiment of a semiconductor laser and its manufacturing method according to the present invention.
(a), (b), and (c) respectively show a top view of a wafer before device separation, a cross-sectional view of this wafer, and a sketch of a laser device after device separation from the wafer. 1... Active region of resonator, 2... Au electrode layer for heat sink, 3... Striped groove portion (portion without Au electrode layer), 5... ... Semiconductor layer, 6 ... Contact electrode layer of Schottky type ohmic electrode, 7 ... High melting point barrier electrode layer (Pt), 7
/...High melting point barrier electrode layer (W or Mo)
, 8... n-type ohmic electrode, 9...
n-type InP substrate, 10... n-type InP cladding layer, 11... InGaAsP active layer, 12...
...p-type InP cladding layer, 13...In
GaAsP cap layer, 14... Striped groove portion (mesa etched portion), 15...
Near the reflective surface of the active region, 16...p-n junction attached to the active layer, 17... side surface of mesa etching. #2 Hard

Claims (1)

[Claims] (1) An ohmic electrode layer including an Au electrode layer for a heat sink and a high melting point barrier electrode layer formed under the Au electrode layer forms an I/C on the surface of the semiconductor mount side. In a certain semiconductor laser, the side surface of the semiconductor on the mount side except for the vicinity of the reflection surface of the resonator is mesa-etched, and the periphery of the Au electrode layer for the heat sink is formed by the high melting point barrier electrode layer. A semiconductor laser characterized by a dot and a dot on the inner side of the periphery. (2. In the semiconductor laser according to claim 1, the ohmic electrode includes a contact electrode layer made of Ti or Or, and the contact electrode layer is under the high melting point barrier electrode layer and is in contact with the semiconductor. A semiconductor laser characterized in that the high melting point barrier electrode layer is made of W or Mo. (3) In the semiconductor laser according to claim 1 or 2, the area other than the upper part of the resonator is A semiconductor laser characterized in that an insulating film is interposed between the surface and the ohmic electrode. (4) A contact electrode layer and a high melting point barrier electrode layer are sequentially formed on the mount side surface of the semiconductor wafer. The first step is to form a first striped window located between the axes of adjacent resonators that are parallel to each other, and a first striped window that is repeated at a repeating pitch of the axial length of the resonator and intersects at right angles to the first striped window. The second striped window is discontinued only above the resonator axis.The discontinuous portion is also connected with narrow stripes and covered with a grid-like photoresist mask as a plating mask, and selective plating of Au is performed to form a quasi-rectangular shape. a third step of forming an Au electrode layer, etching the contact electrode layer through the first and second striped windows into the same shape as the high melting point barrier layer, and using the high melting point barrier layer as a mask to form the contact electrode layer; a fourth step of deep mesa etching of the semiconductor; a fifth step of opening a valve along a groove formed by mesa etching through the second striped window to form a reflective surface of the resonator; and a fifth step of forming a reflective surface of the resonator. A method for manufacturing a semiconductor laser, comprising a sixth step of separating elements along grooves formed by mesa etching through a striped window.