JPH04291979A - Fabrication of semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To improve the characteristics of a semiconductor laser in the information of a semiconductor layer electrode structure by preventing an active laser from a cleavage part upon a high-melting-point contact metal layer from being damaged to prevent the deterioration of device characteristics and make uniform an injected current for improvement of a heat dissipation characteristic. CONSTITUTION:The surface of a semiconductor laser body is covered with an SiO2 film 16, and a stripe window 17 is opened. A high melting point contact metal layer is formed by covering with a Ti film 18 and a Pt film 19. The surface of the metal layer is covered with an Au film. Au plating 21 is formed through selective plating. An Au film 20 of a predetermined width part (in the vicinity of a cleavage portion) on the stripe window is left behind, and the Au film other than the foregoing portion is removed. The high-melting-point contact metal layer (Pt film 19, Ti film) is etched and removed by reactive ion etching (IBE) using the Au plating 21 as a mask.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor light emitting device, and more particularly to a method of forming an electrode structure of a semiconductor laser (LD: laser diode).

0002

2. Description of the Related Art A conventional method for forming electrodes of a semiconductor laser will be explained step by step with reference to FIGS. 14 to 19. (Step 1, FIG. 14) On the n-substrate 51, the n-buffer layer 52
, non-doped active layer 53, p cladding layer 54, and p
Contact layers 55 are sequentially deposited.

(Step 2, FIG. 15) After depositing a dielectric film 56 on the entire surface, stripe windows 57 are opened. (Step 3, FIG. 16) High melting point contact metal layer 58 on the entire surface
Deposit.

(Step 4, FIG. 17) Au plating 59 is formed by selectively plating Au to a thickness of several μm. The Au plating 59 serves to protect the laser active layer from mechanical stress during wire bonding and to improve the dissipation of heat generated in the laser active layer.

(Step 5, FIG. 18) Using the Au plating 59 as a mask, the high melting point contact metal layer 58 is etched and removed. (Step 6, FIG. 19) After selectively etching the dielectric film 56, an element isolation trench 60 is formed in the semiconductor laser body in parallel with the stripe window 57 and deep enough to reach the n-type substrate 51. The device isolation trench 60 is formed in order to measure initial characteristics such as voltage-current characteristics and current-optical characteristics of individual semiconductor laser devices in an array state.

After forming the ohmic contact 61 on the back surface of the n-type substrate 51, A is applied to the portion corresponding to the Au plating 59.
U plating 62 is formed. By cleaving along the cleavage portion 63, the semiconductor laser elements are separated into individual semiconductor laser elements.

[0007]

[Problem to be solved by the invention] In the conventional method, in step 5 (FIG. 18), Au plating 59 is used as a mask,
The high melting point contact metal layer 58 is etched away. Generally, it is difficult to chemically etch high-melting point metals, and if this is done forcibly, there is a high risk of etching the semiconductor of the semiconductor laser body. Therefore, the high melting point contact metal layer 58 is etched by reactive ion etching (RIE) or ion beam etching (
This is done using dry etching such as IBE).

However, since the Au plating 59 is not present in the vicinity of the cleavage portion 63, physical damage caused by RIE or IBE enters the active layer 53 and deteriorates the device characteristics of the semiconductor laser end face. As a result, the threshold current increases and Q-switch oscillation (a phenomenon that oscillates only when a current larger than the normal threshold current is applied) occurs. Furthermore, since the high melting point contact metal layer 58 is not present in the vicinity of the cleavage portion 63, element resistance increases and current is non-uniformly injected. Furthermore, the heat generated in the active layer 53 cannot be efficiently radiated.

[0009] As described above, the conventional example has the problems of lack of reliability and low manufacturing yield. The present invention solves these problems and prevents physical damage to the active layer near the cleavage area during etching of the high-melting point contact metal layer, thereby preventing deterioration of device characteristics and injecting current. uniformity, good heat dissipation characteristics,
It is an object of the present invention to provide a method for manufacturing a semiconductor device, particularly a method for forming an electrode structure of a semiconductor laser, which can improve the characteristics of a semiconductor laser.

0010

Means for Solving the Problems In order to achieve the above object, a method for manufacturing a semiconductor light emitting device according to the present invention is configured as follows. (1) A step of coating the surface of a multilayer semiconductor structure constituting a semiconductor light emitting device of the first invention with a dielectric film, a step of forming striped openings in the dielectric film, and a step of forming a dielectric film including the openings. a step of forming a metal film for contact covering the entire surface of the body membrane; a step of forming a plurality of plating electrodes spaced apart from each other on the metal film located in an area along the stripes of the opening; a process of forming a protective film in the dividing area located above the opening between the plated electrodes to cleave and divide the multilayer semiconductor structure; dry etching the metal film using the plated electrode and the protective film as a mask; The method is configured to include a step of removing the metal film other than the plating electrode and the protective film, and a step of performing cleavage using the dividing region to divide the multilayer semiconductor structure.

(2) A step of coating the surface of the multilayer semiconductor structure constituting the semiconductor light emitting device of the second invention with a dielectric film, a step of forming striped openings in the dielectric film, and a step of forming the openings in the form of stripes. a process of forming a metal film for contacting the semiconductor over the entire surface of the dielectric film including The process of dry etching the metal film using the mask as a mask and removing the metal film other than the plated layer, and selectively removing the continuously formed plated layer in the direction perpendicular to the stripes, and separating the plated layers from each other. The method includes the steps of dividing the structure into a plurality of plating electrodes, and dividing the multilayer semiconductor structure by cleaving the portions located between the plurality of plating electrodes as dividing regions.

0012

In the method for forming an electrode structure according to the present invention, when the high melting point contact metal layer is removed by etching, the high melting point contact metal layer is not exposed in the vicinity of the cleaved portion. That is, the vicinity of the cleavage portion (a predetermined width portion on the striped window) is covered with a highly conductive metal layer. This highly conductive metal layer acts as a protective film during reactive ion etching (RIE) or ion beam etching (IBE), so physical damage caused by etching is localized to the semiconductor laser body, especially near the cleavage area. Prevents it from entering the active layer. As a result, deterioration of element characteristics can be prevented.

[0013] Also, since the part above the stripe window (near the cleavage part) is covered with a high melting point contact metal layer,
A contact electrode is provided over the entire length of the resonator of the semiconductor laser. As a result, the injection current can be made uniform, and the heat generated in the laser active layer can be effectively dissipated.

[0014]

[Embodiment] [First Embodiment] A first embodiment of the present invention will be explained in order of steps with reference to FIGS. 1 to 7. (Step 1, Figure 1) On the n-InP substrate 11, n-InP
Buffer layer (impurity concentration 1 x 1018 cm-2, thickness 2
μm) 12, non-doped InGaAsP active layer (thickness 0
．． 15 μm) 13, p-InP cladding layer (impurity concentration 5×10 cm−2, thickness 1.5 μm) 14, and p-InGaAsP contact layer (impurity concentration 1×10
19cm-2, thickness 0.3μm) 15 was sequentially grown by liquid phase growth method or MOCVD (Metal OrganicC
chemical vapor deposition
) to grow by law. As a result, a semiconductor laser body is formed.

(Step 2, FIG. 2) A SiO2 film (about 3000 Å thick) is formed on the p-InGaAsP contact layer 15.
16 was deposited by thermal CVD method at 400°C, the width was 2.
A μm stripe window 17 is opened.

(Step 3, FIG. 3) A Ti film (thickness 1000 Å) 1 is deposited on the entire surface of the wafer as a high melting point contact metal layer.
8 and a Pt film (thickness: 3000 Å) 19 are deposited by electron beam evaporation.

[0017] An Au film (
A film thickness of 3500 Å) 20 is deposited by electron beam evaporation or resistance evaporation. (Step 4, FIGS. 3 and 4) Patterning for selective plating is performed using ordinary photolithography, and Au plating (thickness: 3 μm) 21 is formed using electrolytic plating.

A p-side ohmic contact is formed by heat treatment at 430° C. for 30 minutes. striped window 17
The Au plating 21 is covered with a photoresist so as to cover the upper part (near the cleavage part), and the part of the Au film 20 not covered with the photoresist is removed by etching.

(Step 5, FIGS. 4 and 5) Using the Au plating 21 as a mask, the Pt film 19 is etched by reactive ion etching (RIE). Ar gas was used as the etching gas for the Pt film 19. In this case, Pt and Au
Since the etching rate of the Pt film 19 is almost the same, the Au part above the stripe window 17 is etched in parallel with the etching of the Pt film 19.
Membrane 20 is also etched. Since the etching rate of Ti is approximately 1/10 of that of Pt and Au, this Au film 20
By stopping the etching when the P
The t-film 19 is etched, leaving only Ti selectively.

The portion of the Au film 20 above the striped window 17 (near the cleavage portion) is removed by etching the Pt film 19, but the Pt film 19 underneath acts as a protective film in the next step. (Step 6, Figure 5, Figure 6) Using the Au plating 21 as a mask,
Ti film 1 is etched by reactive ion etching (RIE).
Etch 8.

CF4 is used as the etching gas for the Ti film 18.
Using gas. In this case, Pt and Au are hardly etched. (Step 7, FIG. 7) Mesa etching of the element isolation groove (approximately 6 μm in depth) 23 is performed using normal photolithography technology.

After making the thickness of the substrate 11 about 100 μm,
After depositing AuGe (film thickness: 500 Å) and Au (film thickness: 2500 Å) on the back surface of the substrate 11 using a resistance vapor deposition method, the film was heated at 380°C.
After 30 minutes of heat treatment, the n-ohmic contact 2
form 4. Patterning for selective plating is performed using ordinary photolithography technology, and Au plating (thickness: 3 μm) 25 is formed using electrolytic plating.

[0023] Cleavage is performed in the cleavage section 22 to separate the semiconductor laser devices into individual semiconductor laser devices, thereby producing products. [Second Embodiment] A second embodiment of the present invention will be explained step by step with reference to FIGS. 8 to 13. (Step 1, FIG. 8) On the n-InP substrate 31,
Buffer layer (impurity concentration 1 x 1018 cm-2, thickness 2
μm) 32, non-doped InGaAsP active layer (thickness 0
．． 15 μm) 33, p-InP cladding layer (impurity concentration 5×10 cm−2, thickness 1.5 μm) 34, and p-InGaAsP contact layer (impurity concentration 1×10
19 cm −2 , thickness 0.3 μm) 35 are sequentially grown by liquid phase epitaxy or MOCVD. As a result, a semiconductor laser body is formed.

(Step 2, FIG. 9) A SiO2 film (about 3000 Å thick) is formed on the p-InGaAsP contact layer 35.
After depositing 36 by thermal CVD method at 400℃,
A μm stripe window 37 is opened.

(Step 3, FIG. 10) A Ti film (thickness: 1000 Å) is formed on the entire surface of the wafer as a high melting point contact metal layer.
38 and a Pt film (thickness: 3000 Å) 39 are deposited by electron beam evaporation.

Patterning for selective plating is performed using ordinary photolithography, and Au plating (thickness: 3 μm) 40 is formed by electroplating so as to cover the portion above the stripe window 37 (near the cleavage portion). 43
Heat treatment is performed at 0° C. for 30 minutes to form a p-side ohmic contact.

(Step 4, FIG. 10, FIG. 11) Au plating 4
0 as a mask, the Pt film 39 is etched by RIE. Ar gas was used as the etching gas for the Pt film 39. In this case, since the etching rates of Pt and Au are almost equal, the etching rate of Pt film 39 is parallel to that of
The u plating 40 is also etched. However, Au
Since the plating 40 has sufficient thickness, there is no problem. As for Ti, most of it can be left because of the difference in etching rate.

(Step 5, FIG. 11, FIG. 12) Au plating 4
0 as a mask, the Ti film 38 is etched by RIE. CF4 gas was used as the etching gas for the Ti film 38. In this case, Pt and Au are hardly etched.

Further, the Au plating 40 existing at the portion above the stripe window 17 is selectively removed using a normal photolithography technique. (Step 6, FIG. 13) Mesa etching of the element isolation groove (approximately 6 μm in depth) 42 is performed using normal photolithography technology.

After making the thickness of the substrate 31 about 100 μm,
After depositing AuGe (film thickness: 500 Å) and Au (film thickness: 2500 Å) on the back surface of the substrate 31 using a resistance vapor deposition method,
After 30 minutes of heat treatment, the n-ohmic contact 4
form 3. Patterning for selective plating is performed using ordinary photolithography technology, and Au plating (thickness: 3 μm) 44 is formed using electrolytic plating.

[0031] Cleavage is performed in the cleavage section 41 to separate the semiconductor laser elements into individual semiconductor laser elements, thereby producing products. In the above embodiment, P
Although reactive ion etching (RIE) was used to etch the T film and Ti film, ion beam etching (
Similar results can be obtained using the IBE) method.

[0032]

According to the present invention, when a high melting point contact metal layer is removed by reactive ion etching (RIE) or ion beam etching (IBE), high conductive metal is removed near the cleavage portion (above the stripe window). The presence of a layer or highly conductive plating can act as a protective layer and prevent physical damage from etching from penetrating the laser active layer. Therefore, deterioration of element characteristics can be prevented.

[0033] Furthermore, since the part above the stripe window (near the cleavage part) is covered with a high melting point contact metal layer,
A contact electrode is provided over the entire length of the resonator of the semiconductor laser. As a result, the injection current can be made uniform, and the heat generated in the laser active layer can be effectively dissipated.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one process of a first embodiment of the present invention.

FIG. 2 is a diagram showing one process of the first embodiment of the present invention.

FIG. 3 is a diagram showing one process of the first embodiment of the present invention.

FIG. 4 is a diagram showing one process of the first embodiment of the present invention.

FIG. 5 is a diagram showing one process of the first embodiment of the present invention.

FIG. 6 is a diagram showing one process of the first embodiment of the present invention.

FIG. 7 is a diagram showing one process of the first embodiment of the present invention.

FIG. 8 is a diagram showing one process of the second embodiment of the present invention.

FIG. 9 is a diagram showing one process of the second embodiment of the present invention.

FIG. 10 is a diagram showing one process of the second embodiment of the present invention.

FIG. 11 is a diagram showing one process of the second embodiment of the present invention.

FIG. 12 is a diagram showing one process of the second embodiment of the present invention.

FIG. 13 is a diagram showing one process of the second embodiment of the present invention.

FIG. 14 is a diagram showing one process of a conventional example.

FIG. 15 is a diagram showing one process of a conventional example.

FIG. 16 is a diagram showing one process of a conventional example.

FIG. 17 is a diagram showing one process of a conventional example.

FIG. 18 is a diagram showing one process of a conventional example.

FIG. 19 is a diagram showing one process of a conventional example.

[Explanation of symbols]

11, 51 N substrate 12, 52 N buffer layer 13, 53 Active layer 14, 54 P cladding layer 15, 55 P contact layer 16, 36 SiO2 film 17, 37 Stripe window 18, 38 Ti film 19, 39 Pt film 20 Au Films 21, 40 Au plating 22, 41 Cleavage portions 23, 42 Element isolation grooves 24, 43 N-ohmic contacts 25, 44
Au plating

Claims (2)

[Claims] 1. A step of coating the surface of a multilayer semiconductor structure constituting a semiconductor light emitting device with a dielectric film, a step of forming striped openings in the dielectric film, and a dielectric film including the openings. a step of forming a metal film for contact covering the entire surface of the opening, a step of forming a plurality of plating electrodes spaced apart from each other on the metal film located in an area along the stripes of the opening, and a step of forming a plurality of plating electrodes at a distance from each other. A process of forming a protective film in the dividing area located above the opening between each other to cleave and divide the multilayer semiconductor structure, and dry etching the metal film using the plating electrode and the protective film as a mask, and removing the plating electrode. and a step of removing a metal film other than a protective film, and a step of performing cleavage using a dividing region to divide a multilayer semiconductor structure. 2. A step of coating a surface of a multilayer semiconductor structure constituting a semiconductor light emitting device with a dielectric film, a step of forming striped openings in the dielectric film, and a dielectric film including the openings. a process of forming a metal film for contacting the semiconductor over the entire surface of the opening, a process of forming a plating layer continuously on the metal film at positions along the stripes of the opening, and a process of forming a metal film using the plating layer as a mask. A process of dry etching to remove metal films other than the plated layer, and a process of selectively removing continuously formed plated layers in a direction perpendicular to the stripes, and multiple plating with a configuration in which the plated layers are separated from each other. 1. A method of manufacturing a semiconductor light emitting device, comprising the steps of dividing into electrodes, and dividing a multilayer semiconductor structure by cleaving the portions located between the plurality of plated electrodes as dividing regions.