JPS59219975A - Cleaving method of semiconductor laser - Google Patents

Abstract

PURPOSE:To cleave a wafer efficiently with high yield in a short time by forming a groove from the substrate side of the wafer and giving an ultrasonic vibration when shaping a Fabry-Perot resonator surface. CONSTITUTION:Epitaxial layers 3 of multilayers are grown on a crystalline substrate 2 in GaAs or InP, and metallic electrodes 1, 4 are evaporated. Grooves 5 are formed along a crystal axis from the substrate side of a wafer through chemical etching or ion etching or the like. The wafer is dipped in a beaker in which water is entered, water is given an ultrasonic vibration together with the beaker, and the whole wafer is cloven efficiently at a time along the grooves. An edge is applied to a slender cylindrical substrate 6 obtained and the substrate is cut out into several laser chip. Since there is no flaw in a resonator 9 in the laser chip 8, the surface of the resonator is changed into a fine mirror surface and the reflectivity of beams is improved, laser oscillation threshold currents are reduced, and yield can be enhanced remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an interosseous method used for fabricating a Fabry-Perot cavity surface of a semiconductor laser.

Conventional Structure and Problems The resonator of a semiconductor laser has conventionally been a Fapry-Perot type resonator using a cleavage plane of a crystal. recently,
Distributed feedback that performs optical feedback using a diffraction grating (commonly known as D
There are reports of obtaining laser oscillation using resonators such as FB) or distributed reflection type (commonly known as DBR), but semiconductor lasers of this type still have a low yield and lack productivity.

Therefore, Fabry-Perot semiconductor lasers using interfold surfaces are currently the mainstream because of their ease of manufacturing.

To explain the method for manufacturing a Noah-Priperot type semiconductor laser, a multilayer epitaxial crystal is formed on a substrate with interosseous crystalline properties (e.g., GaAs or InP), and a metal electrode with ohmic properties (e.g., Au-
(Zn, etc.) is deposited.

Next, the substrate side is polished to a thickness of about 100 μm. This is a necessary step to facilitate the interosseous interossification in the next interosseous process. After polishing the wafer,
An ohmic metal electrode (for example, Au
-8n, etc.) is deposited. Thereafter, by applying a sharp blade to the crystal, it is cut into a long and thin rod shape with a width of 0.2 to osmm between the bones. The inter-fold plane of this rod-shaped crystal substrate becomes the resonator plane of the laser, and therefore the width of this rod corresponds to the length of the resonator. In this method, when applying a sharp blade to interfold the crystal, The direction of the bone must be parallel to the crystal axis, but if this is even slightly off, the bones will not intersect properly and a clean mirror surface will not be obtained. If the interfold surface is not a clean mirror surface and has scratches, etc., when used as a laser cavity surface, the light reflectance will decrease, the optical gain will decrease, and the laser oscillation threshold current will increase, making it impractical. This results in a significant decrease in yield. Therefore, it is necessary to accurately align the direction of the blade and the crystal axis to intersect the bone, but this is extremely difficult.

This is because the inter-folding of a crystal is done for each atom that makes up the crystal, so the direction of the blade and the crystal axis must be aligned with the precision of the atomic lattice constant, that is, the precision of several people. It is from. Therefore, when applying a blade to interfold, after aligning the direction of the blade and the crystal axis to a certain extent,
Try touching the blade lightly to the crystal. If the direction of the blade and the crystal axis are precisely aligned, the crystal can be easily and silently inserted between the bones and a beautiful mirror surface can be obtained. If they are not aligned, the bones will not be aligned by applying light pressure, and if you force the folds to move between the folds, the surface between the folds will not be a clean mirror surface and will have burr-like jagged edges. Therefore, try applying the blade lightly several times while changing the direction of the blade little by little.
This must be repeated until the bone is moved silently. This work was extremely time consuming and inefficient, and required a certain degree of skill to master the subtle sensation of the hand holding the blade as it silently intersected the bones. Furthermore, when the bone is interboned without making a sound, the interfold surface becomes a beautiful mirror surface, but the interfold surface inevitably gets scratched at the part where the blade touches, which reduces the yield.

A blade is applied to the elongated rod-shaped crystal substrate obtained in this manner and cut into individual laser chips, thereby completing one laser chip. Since the size of one laser chip is 0.2 to 0.3 πm square, one
Several hundred laser chips can be obtained from (approximately 1QmM square). Therefore, it was necessary to perform the interosseous surgery several hundred times. Furthermore, since the distance between the bones is approximately 0.2 to 0.3 ffff, these operations must be carried out under a microscope, which is extremely inefficient. With this method, it takes a lot of time to align the direction of the blade and the crystal axis in parallel and align the bones.

(2) A certain degree of skill is required to master the subtle sensation of the hand holding the blade when it is silently inserted between the bones. (3)
Scratches appear on the interfold surface where the blade hits, reducing yield. (4) To make a laser chip, a blade must be applied several hundred times to cut the bone, which takes a lot of time. (There was a problem in that the workability was poor because the interosseous examination had to be performed under a warm microscope.

Purpose of the Invention In view of the above-mentioned problems of the prior art, the object of the present invention is to perform interosseous surgery efficiently, in a short period of time, and with a high yield without requiring any skill at all.

Structure of the Invention In this invention, a groove is formed from the substrate side of the sea urchin, and the entire sea urchin is interosseous at once by applying ultrasonic vibration to the wafer.

Description of examples Embodiments of the invention will be described with reference to the drawings.

In Figure 1, a multilayer epitaxial layer 3 is grown on a GaAs or InP crystal substrate 2, an ohmic metal electrode 4 is deposited, the substrate side is polished to a thickness of about 100 μm, and an ohmic layer is formed on the substrate side. It shows the percentage of sea urchins deposited with a metal electrode 1 having a certain property. Grooves are formed along the crystal axis from the substrate side of this wafer. The situation is shown in Figure 2. The groove 6 is formed by chemical etching or ion etching. The thickness from the bottom of the groove 6 to the opposite side of the substrate needs to be thick enough not to break during the etching and cleaning process, and thin enough to be able to be penetrated by ultrasonic vibration. A suitable thickness is 30 μm.

By doing this, the mechanical strength of only the groove portion of the wafer is weakened, and when ultrasonic vibration is applied, the groove is formed along the crystal axis, so the wafer is easily interosseous along the groove. .

When applying ultrasonic vibrations to a wafer, the wafer is immersed in a beaker filled with water, and the beaker itself is subjected to ultrasonic vibrations so that the longitudinal waves of the ultrasonic vibrations travel through the water and are efficiently transmitted to the wafer. By doing this, the vibrations are transmitted to all parts of the wafer, and the entire wafer is efficiently moved along the grooves at once.

According to this method, the entire wafer can be processed at one time, so it is very efficient and the process time can be shortened. Further, as described in the conventional example, this method does not require any skill to apply the blade to the bone.

6 in FIG. 3 is the elongated rod-shaped substrate thus obtained. According to this method, 1. Unlike the inter-fold surfaces 7 forming the laser resonator, the entire surface becomes a clean mirror surface, unlike the inter-fold surfaces 7 formed by the blade, so that the yield 9 can be significantly improved.

It is also better to form the groove 6 in a V shape and apply ultrasonic vibration because the stress will be concentrated at the apex of the V.

Moreover, if the groove is made into a V shape, the bones will be interposed at the apex of the V, so the width of the long thin bar-shaped substrate between the bones, that is, the length of the laser resonator, will be a constant dimension, and when it is made into one laser chip. There is no variation in laser cavity length, further improving yield. Note that the V-groove may be formed using an anisotropic etching solution.

FIG. 4 shows how the elongated rod-shaped substrate 6 thus obtained is cut into individual laser tips by applying a blade to it. The resonator surface 9 of the laser chip 8 cut out in this way has no scratches and has a clean mirror surface, which increases the reflectance of light, reduces the laser oscillation threshold current, and significantly improves the yield.

Furthermore, FIG. 6 shows a state in which similar grooves are also formed in a direction perpendicular to the surface on which the Fabry-Perot resonator is formed. After forming such grooves, by applying ultrasonic vibration to the wafer in the same manner as described above, it is possible to separate the individual laser chips at the same time as separating the bones. This eliminates the need for cutting with a blade as shown in FIG. 4, further reducing process time and improving yield.

In addition, in addition to applying ultrasonic vibration by placing a wafer in water and applying bee force between the bones, applying sonic vibration in the air,
A longitudinal wave may be transmitted to the wafer using air as a medium to perform the interosseous treatment.

Effects of the Invention As described above, when the present invention is used in the inter-fold process of a 7-apple Perot type semiconductor laser, the following effects can be obtained.

(1) Process time can be shortened because the entire wafer can be interossified at once by ultrasonic vibration. [2) Since the inter-osseous treatment is performed using ultrasonic vibration without using a blade, the inter-fold surface becomes a clean mirror surface over the entire surface, improving the yield.

Performing interosseous surgery using inverted sonic vibrations does not require the same level of skill as when applying a sword blade to perform interosseous interossification, and does not require poor workability such as performing under a microscope. (If the four-channel groove is formed in a V-shape, the laser resonator length can be made constant, so there is no variation in the resonator length, which further improves the yield.

[Brief explanation of drawings]

Figure 1 is a perspective view of a wafer in front of the rib cage, where multiple epitaxial layers are grown on a GaAs or InP crystal substrate and an ohmic metal electrode is deposited on the substrate side. FIG. 3 is a perspective view of a wafer in which grooves are formed repeating the length of the 77 Prebellow resonator from the side; FIG.
The figure shows how individual laser chips are cut out by applying a blade to an elongated rod-shaped substrate, and FIG. 6 shows a perspective view of a wafer in which grooves are also formed in a direction perpendicular to the Noabry-Perot resonator surface. 2...GaAs or InP crystal substrate,
3...Multilayer epitaxial layer, 5...
・A groove repeating the length of a Fabry-Bello resonator formed along the crystal axis by chemical etching or ionoetching, etc., 6... A long and thin rod-shaped crystal substrate interposed between bones along the groove, 7・・・・・・Fabry-Perot interosseous surface which becomes the resonator surface, 8・・・・・・One laser tip cut out from a long and thin rod-shaped crystal substrate, 9・・・・・・
・Laser Fabry-Perot cavity surface. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 5

Claims (3)

[Claims] (1) When folding a wafer containing a substrate crystal and an epitaxial layer grown thereon to form a Fapley-Perot resonator surface, grooves are formed repeatedly the length of seven Aply-Perot resonators from the substrate side of the wafer. After forming the
1. A semiconductor laser interosseous method, characterized in that the wafer is subjected to ultrasonic vibration to create inter-folds along the grooves. (2) The interosseous method for a semiconductor laser according to claim 1, wherein a similar groove is also formed in a direction perpendicular to the Fabry-Perot cavity surface. (3) The semiconductor laser interosseous method according to claim 1, wherein the groove is formed in a V-shape.