JP2783240B2 - Semiconductor laser device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for passivating a reflection surface of a semiconductor laser device, which is suitable for mass production and integration with electronic circuits. 2. Description of the Related Art Semiconductor laser devices have excellent features not found in other lasers, such as small size, high efficiency, and low power consumption, and are widely applied to light sources for optical communication and optical disk pickups. It has become. One of the reasons for the rapid commercialization of semiconductor lasers is that the semiconductor laser cavity reflection surface is subjected to passivation treatment of a dielectric or the like, thereby significantly reducing the deterioration phenomenon of the laser element caused by the end face deterioration. There are things. There are many examples of reflective surface passivation processing (for example, K. Kressel et al., RCA Review Vol. 36, No. 2,
230, 1975 (K. Kressel et al., RCA Review Vol. 36,
No.2, p.230, 1975), F.R.Nash, et al., Applied Physics Letter 35, 12, 905, 1979
(FRNash et al. Appl. Phys. Lett. Vol. 35 No. 12,
P.905,1979)). [0003] However, the reflection surface for a resonator of a conventional semiconductor laser is manufactured by a cleavage surface using a specific orientation of a crystal. Therefore, passivation processing such as coating of a dielectric film on a reflection surface for improving the reliability of laser has been performed after bonding to a cleaved chip state or a stem. Therefore, the laser reflection surface passivation process has a serious problem that its workability is extremely poor and its mass productivity is poor. An object of the present invention is to solve the above problems and to provide a semiconductor laser reflecting surface passivation method which is excellent in workability and mass productivity. [0005] In order to achieve the above object, in the present invention, passivation of a laser reflecting surface is performed by the following method. First, the laser double hetero layer is processed almost vertically by, for example, a chemical etching method or a dry etching method to form a laser reflecting surface. Next, a passivation dielectric film is formed on the entire surface in the wafer state as it is. In the following embodiments, an example of SiO ₂ is shown as the passivation dielectric film, but it goes without saying that other well-known dielectric films may be used. At this time, the passivation process of the reflection surface is performed by the dielectric film going into the concave portion forming the reflection surface. Next, using a photolithography technique, the dielectric film on the surface electrode or the like is removed to expose the electrode surface. According to the present invention, the passivation of the laser reflecting surface can be performed in the wafer state, so that the workability and mass productivity are remarkably improved as compared with the conventional method in the chip state. Hereinafter, the present invention will be described with reference to examples. FIG. 1 shows an embodiment of the present invention.
Sectional view (a) in the light traveling direction of a GaAS-GaAlAs-based semiconductor laser having a Substrate Planar (CSP for short) structure, and
It is a sectional view (b) of a perpendicular direction. To explain each part, 1
Is an n-type GaAs substrate (Si doped, ~ 1 × 10 ¹⁸ cm ^-3 , (100)
A band-like groove 2 having a width of about 5 μm and a depth of about 1.3 μm is formed on the substrate surface, and an n-type Ga _0.6 Al _0.4 As cladding layer 3 (Te doped, n〜1 × 10 ¹⁸ cm ^{−) is formed} thereon. ³ , About the thickness outside the groove
0.3 μm) 4, Ga _0.86 Al _0.14 As active layer 4 (undoped,
About 0.06 μm), p-type Ga _0.6 Al _0.4 As cladding layer 5 (Zn-doped, p105 × 10 ¹⁷ cm ^-3 , about 2 μm thick) n-type GaAs cap layer 6 (Te-doped, nｎ1 × 10 ¹⁸⁾ cm ^-3 , thickness about 0.5μ
m) is formed. Reference numeral 7 denotes a region which is inverted to the p-type by Zn diffusion, and has a structure in which current flows efficiently through this portion to the active region. The passivation film 10 of the present invention is formed on the resonator reflecting surface. In this embodiment, the passivation film 10 is a SiO ₂ film formed by a sputter coating method, and is about 230 nm. Next, features of the present invention will be described with reference to FIG. FIG. 2 shows a method of manufacturing the device according to the embodiment of the present invention shown in FIG.
In the semiconductor laser device fabrication process, after laminating each semiconductor layer on a semiconductor substrate, a p-side electrode 8 was formed, and a cavity reflection surface 11 was formed by a reactive ion beam etching method using a photoresist film as a mask ( FIG. 2 (a)). Chlorine Cl ₂ is used as the etching gas, and the pressure is about 1 × 10 ^-1 Pa,
Etching was performed at an acceleration voltage of 400V. The etching depth is about 7 μm. The angle of the reflecting surface could be formed almost perpendicularly. Next, by the sputter coating method,
SiO ₂ 10 was formed on the entire surface (FIG. 2B). At this time, SiO ₂ wrapped around the resonator reflection surface, and a passivation film was formed at a speed of about 60% with respect to the flat surface portion. The passivation film thickness on the reflecting surface was about 230 nm. As a method of sputter coating, target is SiO ₂
And in a Ar atmosphere by a high frequency sputtering method. The feature of the sputter coating is that a dielectric film can be formed in the inside of a groove or the like as described above. Next, a photoresist mask was formed by photolithography, and SiO ₂ on the p-electrode was removed by etching. A mixture of hydrofluoric acid and ammonium fluoride was used as an etchant. Continued to,
After polishing and etching the back surface to make the wafer thickness about 250 μm, an n-side electrode was formed (FIG. 2C). This semiconductor laser oscillated in the transverse fundamental mode up to an optical output of about 10 mW at a threshold current value of about 50 mA and an oscillation wavelength of about 780 nm. As described in the present embodiment, the passivation process of the semiconductor laser reflecting surface is performed at the wafer stage, so that the manufacturing process is significantly simplified as compared with the conventional method performed in a chip state. As described above, according to the present invention, the passivation processing of the semiconductor laser reflecting surface can be performed before the chip is divided, and the semiconductor laser element manufacturing process is significantly improved. Further, the present invention is applicable not only to GaAlAs-based materials but also to other materials, optical integrated devices, optical / electronic integrated devices, and the like. As described above, the present invention provides a method for passivating the reflection surface of a semiconductor laser in a wafer state and removing unnecessary dielectric films on the electrode surface and the like. Compared with the conventional method of performing a passivation process in a chip state or the like, the element manufacturing process is remarkably improved, and a manufacturing process suitable for mass production has become possible. Also,
The present invention can be applied to an optical integrated device or an optical / electronic integrated device in which a laser and an electronic circuit are integrated, and its practical effect is great.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) is a cross-sectional view parallel to a light traveling direction of a semiconductor laser showing an embodiment of the present invention, and FIG. 1 (b) is a cross-sectional view in a vertical direction thereof. is there. FIG. 2 is a cross-sectional view showing an element manufacturing process of the semiconductor laser of the present invention. [Description of Signs] 1 ... n-GaAs substrate, 3 ... n-Ga _0.6 Al _0.4 As cladding layer, 4 ...
Ga _0.86 Al _0.14 As active layer, 5: p-Ga _0.6 Al _0.4 As clad layer, 10: reflection surface SiO ₂ passivation film, 11: laser reflection surface.

Claims (1)

(57) [the claims] 1. A semiconductor substrate, a plurality of semiconductor layers stacked on the semiconductor substrate to form a resonator, an electrode formed on an upper surface of the semiconductor layer at a distance from an end of the upper surface, and an upper surface of the semiconductor layer. A dielectric film formed so as to cover a region extending to the side surface of the semiconductor substrate through the end face of the resonator, wherein the dielectric film covers an upper surface of a peripheral portion of the electrode on the resonator end face side; A semiconductor laser device formed, wherein a side surface of the semiconductor substrate includes a region where the dielectric film is not formed.