Method for manufacturing a laser chip

Abstract

Method for producing a laser chip (140) comprising the following steps: - Providing a semiconductor wafer (100) having a top side (101) and a bottom side (102), wherein the semiconductor wafer (100) has a plurality of integrated laser diode structures (141) arranged one behind the other along a predetermined fracture direction (10); - creating a plurality of depressions (200, 300) arranged one behind the other along the fracture direction (10) on the upper side (101) of the semiconductor wafer (100), wherein one of the depressions (200, 300) is arranged between each two adjacent laser diode structures (141), wherein each of the recesses (200, 300) has a front boundary surface (210) and a rear boundary surface (220) successively in the fracture direction (10), wherein in at least one of the recesses (200, 300) the rear boundary surface (220) is inclined relative to the upper side (101) of the semiconductor wafer (100) by an angle (221) between 95° and 170°, wherein at least one of the depressions (200, 300) is arranged closer to a laser diode structure (141) located closest in front of the depression (200, 300) in the fracture direction (10) than to a laser diode structure (141) located closest behind the depression (200, 300) in the fracture direction (10), wherein the distance (245) between the depression (200, 300) and the laser diode structure (141) closest to the depression (200, 300) in the fracture direction (10) is at least four times as large as the distance (240) between the depression (200, 300) and the laser diode structure (141) closest to the depression (200, 300) in the fracture direction (10), preferably at least eight times as large; - breaking the semiconductor wafer (100) in the breaking direction (10) at a breaking plane (20) oriented perpendicular to the upper side (101) of the semiconductor wafer (100) and passing through the recesses (200, 300).

Description

[0001] The present invention relates to a method for producing a laser chip according to claim 1.

[0002] Semiconductor laser chips with integrated laser diodes are known from the prior art. It is known to produce a plurality of such laser chips simultaneously in joint operations by forming several laser diode structures in a regular matrix arrangement on an extended semiconductor wafer. Only after completion of the processing are these structures separated by dicing the semiconductor wafer. The semiconductor wafer is dicing by controlled breaking of the semiconductor wafer. Two opposing fracture surfaces of the laser chips formed in this way form mirror facets of the laser chips.

[0003] To determine the fracture planes along which the semiconductor wafer is fractured, it is known to create recesses (skips) on the surface of the semiconductor wafer before breaking the wafer. However, it has been shown that during the breaking of the semiconductor wafer, dislocations and other crystal defects can propagate from these recesses in the crystal of the semiconductor wafer, extending into the active regions of the laser diode structures and reducing the quality of the resulting mirror facets. This can result in increased threshold currents, reduced transconductance, defects in image quality, reduced efficiency, and a reduced component lifetime.

[0004] US 2011 / 0 292 956 A1, US 2011 / 0 292 959 A1, US 2009 / 0 185 594 A1, JP 2012 - 243 866 A, US 2009 / 0 137 098 A1 and US 2009 / 0 262 771 A1 each describe methods for producing laser chips which comprise breaking a semiconductor wafer.

[0005] One object of the present invention is to provide a method for producing a laser chip. This object is achieved by a method having the features of claim 1. Various further developments are specified in the dependent claims.

[0006] A method for producing a laser chip comprises steps of providing a semiconductor wafer with a top side and a bottom side, wherein the semiconductor wafer has a plurality of integrated laser diode structures arranged one behind the other along a defined fracture direction, for creating a plurality of depressions arranged one behind the other along the fracture direction on the top side of the semiconductor wafer, wherein each depression has a front boundary surface and a rear boundary surface following one another in the fracture direction, wherein in at least one depression the rear boundary surface is inclined by an angle between 95° and 170° with respect to the top side of the semiconductor wafer, and for breaking the semiconductor wafer in the fracture direction at a fracture plane oriented perpendicular to the top side of the semiconductor wafer and running through the depressions.

[0007] Advantageously, in this method, the rear boundary surface of the at least one depression arranged on the upper side of the semiconductor wafer, which is inclined at an angle relative to the upper side of the semiconductor wafer, ensures that dislocations and other crystal defects emanating from the rear boundary surface of the depression propagate in the crystal of the semiconductor wafer toward the underside of the semiconductor wafer and thus cannot penetrate into a region of the semiconductor wafer that is critical for the quality of the laser chip obtainable by the method. This advantageously reduces the risk of deterioration of the properties of the laser chip obtainable by the method due to crystal defects formed during the breaking of the semiconductor wafer.

[0008] It is preferred that the rear boundary surfaces of as many or even all of the recesses arranged one behind the other on the upper side of the semiconductor wafer be inclined relative to the upper side of the semiconductor wafer at an angle of between 95° and 170°. This reduces the risk of crystal defects propagating into critical areas of the semiconductor wafer for all correspondingly designed recesses on the upper side of the semiconductor wafer.

[0009] A recess is arranged between each of two adjacent laser diode structures. This has been proven to reliably define the fracture plane at which the semiconductor wafer is fractured, without causing excessive damage to the semiconductor wafer due to an excessive number of recesses.

[0010] At least one recess is arranged closer to a laser diode structure located closest in front of the recess in the fracture direction than to a laser diode structure located closest behind the recess in the fracture direction. This means that the distance between the laser diode structure located closest in front of the recess in the fracture direction and the recess is smaller than the distance between the recess and the laser diode structure located closest behind the recess in the fracture direction. This advantageously leaves sufficient space for crystal defects emanating from the rear boundary surface of the recess to run toward the underside of the semiconductor wafer into a substrate of the semiconductor wafer without penetrating a region of the semiconductor wafer that is critical for the quality of the laser diode structure located closest behind the recess in the fracture direction.This advantageously reduces the risk that the laser diode structure closest to the recess in the fracture direction is damaged by crystal defects emanating from the recess during the breakage of the semiconductor wafer.

[0011] In a preferred embodiment of the method, several or even all of the depressions on the upper side of the semiconductor wafer are arranged correspondingly closer to the laser diode structure that is closest in front of the respective depression in the fracture direction than to the laser diode structure that is closest in the fracture direction behind the respective depression.

[0012] The distance between the recess and the laser diode structure closest to the recess in the fracture direction is at least four times as large as the distance between the recess and the laser diode structure closest to the recess in the fracture direction, preferably even at least eight times as large. Advantageously, it has been proven that such a large distance between the recess and the laser diode structure closest to the recess in the fracture direction can effectively reduce the risk of damage to the laser diode structure closest to the recess due to crystal defects emanating from the rear boundary surface of the recess during fracturing of the semiconductor wafer.

[0013] In one embodiment of the method, each of the laser diode structures has a resonator oriented perpendicular to the fracture direction. As a result, mirror facets or laser facets of the thus separated laser chips are formed at the fracture plane during the fracture of the semiconductor wafer. These facets can advantageously be of high quality. Due to the design of the recess arranged on the upper side of the semiconductor wafer with the rear boundary surface inclined at an angle relative to the upper side of the semiconductor wafer, there is only a low risk of the facets being damaged by crystal defects emanating from the recess during the fracture of the semiconductor wafer.

[0014] In one embodiment of the method, the recesses are created by scribing or using a laser. Advantageously, both methods allow precise control of the resulting shape of the recesses, in particular precise control of the inclination of the rear boundary surface of the recess.

[0015] In one embodiment of the method, this comprises a further step of creating an edge notch arranged in the fracture plane at a leading edge of the semiconductor wafer in the fracture direction. Advantageously, the edge notch can serve as a starting point for the fracture that continues along the fracture plane in the fracture direction through the semiconductor wafer during the fracture of the semiconductor wafer. The edge notch can also be created, for example, by scribing or by means of a laser.

[0016] In one embodiment of the method, this comprises a further step of creating a trench on the underside of the semiconductor wafer, extending in the fracture direction and arranged in the fracture plane. Advantageously, creating the trench on the underside of the semiconductor wafer can facilitate the fracture of the semiconductor wafer.

[0017] In one embodiment of the method, the trench is created by sawing, using a laser, or through an etching process. Advantageously, these methods allow for precise, cost-effective, and rapid trench creation.

[0018] In one embodiment of the method, this comprises a further step of creating a plurality of recesses arranged one behind the other in the fracture plane and along the fracture direction on the underside of the semiconductor wafer. Advantageously, such recesses arranged on the underside of the semiconductor wafer can also facilitate the breaking of the semiconductor wafer at the fracture plane.

[0019] In one embodiment of the method, the depressions on the underside of the semiconductor wafer are formed as a mirror image of the depressions on the top side of the semiconductor wafer. This means that in at least one, but preferably in many or even all of the depressions on the underside of the semiconductor wafer, a rear boundary surface in the fracture direction is inclined relative to the underside of the semiconductor wafer by an angle of between 95° and 170°. The result of this is that crystal defects emanating from the rear boundary surface of a depression formed in this way on the underside of the semiconductor wafer run through the semiconductor wafer essentially in a direction perpendicular to the underside of the semiconductor wafer and can thereby intercept crystal defects emanating from a depression arranged on the top side of the semiconductor wafer.The depressions arranged on the underside of the semiconductor wafer can be positioned exactly below the depressions arranged on the top side of the semiconductor wafer in the fracture direction. However, the depressions arranged on the top side of the semiconductor wafer and the depressions arranged on the underside of the semiconductor wafer can also be offset from one another in the fracture direction.

[0020] In one embodiment of the method, the rear boundary surface of at least one recess is inclined relative to the top side of the semiconductor wafer by an angle between 100° and 160°, preferably by an angle between 120° and 145°. Experiments have shown that such an inclination of the rear boundary surface relative to the top side of the semiconductor wafer can achieve a particularly effective deflection of crystal defects emanating from the rear boundary surface of the recess toward the underside of the semiconductor wafer.

[0021] In one embodiment of the method, at least one depression in the direction perpendicular to the upper side of the semiconductor wafer has a depth of between 5 µm and 80 µm, preferably between 15 µm and 70 µm, particularly preferably between 25 µm and 55 µm. Preferably, several or all of the depressions on the upper side of the semiconductor wafer are formed in this way. Experiments have shown that depressions of this depth can achieve particularly effective definition of the fracture plane without causing excessive damage to the crystal of the semiconductor wafer due to the creation of the depression.

[0022] In one embodiment of the method, in at least one recess, the front boundary surface is inclined relative to the upper side of the semiconductor wafer by an angle between 75° and 95°, preferably by an angle between 85° and 95°. This means that the front boundary surface of the recess is arranged substantially perpendicular to the upper side of the semiconductor wafer. Preferably, several or all of the recesses on the upper side of the semiconductor wafer are formed in this way. It has been shown that during the breaking of the semiconductor wafer, essentially no crystal defects emanate from the front boundary surfaces of the recesses, so that they do not have to be inclined relative to the upper side of the semiconductor wafer. The substantially perpendicular arrangement of the front boundary surfaces relative to the upper side of the semiconductor wafer can advantageously be produced particularly simply and cost-effectively.

[0023] In one embodiment of the method, at least one depression has a length at its base in the fracture direction that lies between 5 µm and 100 µm, preferably between 15 µm and 80 µm, particularly preferably between 20 µm and 50 µm. Preferably, several or even all of the depressions on the upper side of the semiconductor wafer are formed in this way. Experiments have shown that by creating depressions of this length on the upper side of the semiconductor wafer, the fracture plane for breaking the semiconductor wafer can be defined particularly effectively, without the creation of the depressions being accompanied by excessive damage to the crystal structure of the semiconductor wafer.

[0024] In one embodiment of the method, at least one depression has a shoulder adjoining the rear boundary surface. The shoulder has a shoulder surface parallel to the upper side of the semiconductor wafer, which shoulder adjoins the rear boundary surface. In a preferred embodiment of the method, several or even all of the depressions on the upper side of the semiconductor wafer are formed in this way. During breakage of the semiconductor wafer at the fracture plane, crystal defects can emanate from the shoulder surface of the shoulder of the depression, which continue essentially perpendicular to the shoulder surface through the crystal of the semiconductor wafer, i.e. also perpendicular to the upper side of the semiconductor wafer. The crystal defects emanating from the shoulder surface thus propagate towards the underside of the semiconductor wafer without penetrating into regions of the semiconductor wafer that are critical for the quality of the laser chip obtainable by the method.Rather, crystal defects originating from the shoulder surface of the recess can still absorb crystal defects originating from the rear boundary surface of the recess, whereby the risk of crystal defects originating from the rear boundary surface of the recess penetrating into areas of the semiconductor wafer that are critical for the quality of the laser chip obtainable by the process is further reduced.

[0025] In one embodiment of the method, the shoulder surface has a length in the fracture direction between 5 µm and 100 µm, preferably a length between 15 µm and 80 µm, particularly preferably a length between 20 µm and 50 µm. It has been shown that forming the shoulder surface with such a length is particularly effective.

[0026] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings. In each case, in a schematic representation, Fig. 1 is a perspective view of a portion of a semiconductor wafer; Fig. 2 a sectional view of the semiconductor wafer with first upper depressions; Fig. 3 a sectional view of the semiconductor wafer with second upper depressions; and Fig. 4 a sectional view of the semiconductor wafer with additional lower recesses.

[0027] Fig. 1 shows a schematic perspective view of a portion of a semiconductor wafer 100. The semiconductor wafer 100 is formed as a substantially flat wafer having a top side 101 and a bottom side 102 opposite the top side 101. The semiconductor wafer 100 may comprise a plurality of different layers that were epitaxially grown on one another in a growth direction 12 extending from the bottom side 102 to the top side 101 of the semiconductor wafer 100. The semiconductor wafer 100 may have larger dimensions in the lateral direction than is shown in Fig. 1. The semiconductor wafer 100 can be formed, for example, by a complete wafer or by a part of a wafer.

[0028] A plurality of laser chips 140 are to be formed from the semiconductor wafer 100 by dicing the semiconductor wafer 100. For this purpose, the semiconductor wafer 100 has a plurality of integrated laser diode structures 141. The individual laser diode structures 141 are arranged in rows that are arranged next to one another in a fracture direction 10 of the semiconductor wafer 100 that is perpendicular to the growth direction 12 and extend in a longitudinal direction 11 that is perpendicular to the fracture direction 10 and the growth direction 12.

[0029] Each of the rows of laser diode structures 141 has a rib 110 extending in the longitudinal direction 11 on the top side 101 of the semiconductor wafer 100. The ribs 110 can also be referred to as ridges. The ribs 110 are formed by removing parts of the semiconductor wafer 100 on the top side 101 of the semiconductor wafer 100 in the regions outside the ribs 110, for example, by means of an etching process. The part of the semiconductor wafer 100 removed on the top side 101 of the semiconductor wafer 100 can, for example, comprise an upper cladding layer, whereby the upper cladding layer remains only in the region of the ribs 110. The ribs 110 can, for example, have a width of between 1.8 µm and 40 µm in the fracture direction 10. The side surfaces of the ribs 110 extending parallel to the longitudinal direction 11 and the growth direction 12 can be passivated, for example with silicon nitride.On the upper side of the ribs 110 parallel to the fracture direction 10 and the longitudinal direction 11, a metallization can be arranged, which serves for the electrical contacting of the laser chips 140 to be formed from the semiconductor wafer 100 and which can, for example, have a thickness of approximately 1 µm.

[0030] Between each of the two ribs 110 located adjacent to one another in the fracture direction 10 on the top side 101 of the semiconductor wafer 100, a mesa trench 120 extending in the longitudinal direction 11 is arranged. The mesa trenches 120 are formed as channel-shaped depressions on the top side 101 of the semiconductor wafer 100 and can extend in the direction opposite to the growth direction 12, for example, to below a pn junction of the semiconductor wafer 100. The mesa trenches 120 can, for example, have substantially rectangular cross-sections. In the fracture direction 10, the mesa trenches 120 can, for example, have a width of approximately 50 µm.

[0031] To divide the semiconductor wafer 100 into the individual laser chips 140, the semiconductor wafer 100 must be divided at fracture planes 20 perpendicular to the longitudinal direction 11 and at further fracture planes 30 perpendicular to the fracture direction 10. The further fracture planes 30 extend through the mesa trenches 120. By dividing the semiconductor wafer 100 at the fracture planes 20, laser bars are formed, each comprising a plurality of laser diode structures 141 arranged side by side in the fracture direction 10. The laser bars are then divided at the further fracture planes 30, thereby forming the individual laser chips 140.

[0032] By splitting the semiconductor wafer 100 at the fracture planes 20, mirror surfaces of resonators 142 of the individual laser diode structures 141 are formed. To form high-quality mirror surfaces, the semiconductor wafer 100 is split at the fracture planes 20 by breaking the semiconductor wafer. Ideally, this allows for the formation of atomically smooth fracture edges, resulting in high-quality mirror surfaces of the resonators 142.

[0033] The breaking of the semiconductor wafer 100 at the fracture planes 20 takes place in the fracture direction 10 from a side surface of the semiconductor wafer 100 located at the front in the fracture direction 10 and perpendicular to the fracture direction 10 to a side surface of the semiconductor wafer 100 located at the rear in the fracture direction 10 and perpendicular to the fracture direction 10. In the schematic representation of the Fig. 1, the breaking of the semiconductor wafer 100 occurs, for example, from the visible front side surface to the hidden rear side surface of the semiconductor wafer 100.

[0034] The breaking of the semiconductor wafer 100 at the fracture planes 20 takes place in each case starting from a defined predetermined breaking point on the side surface of the semiconductor wafer 100 located at the front in the fracture direction 10. In order to guide the fracture of the semiconductor wafer 100 at the respective desired fracture plane 20, further weakenings are provided on the upper side 101 of the semiconductor wafer 100 along the desired fracture planes 20.

[0035] Fig. 2 shows a schematic sectional side view of a part of the semiconductor wafer 100. The semiconductor wafer 100 is cut at one of the fracture planes 20. The desired fracture direction 10 for breaking the semiconductor wafer 100 at the fracture plane 20 extends in the schematic representation of the Fig. 2 from left to right, so that one in the representation of the Fig. 2 left side surface of the semiconductor wafer 100 forms a side surface of the semiconductor wafer 100 which is located at the front in the fracture direction 10.

[0036] As a starting point for the fracture of the semiconductor wafer 100, an edge notch 170 is created at a front edge 160 in the fracture direction 10 in the transition region between the side surface of the semiconductor wafer 100 located at the front in the fracture direction 10 and the top side 101 of the semiconductor wafer 100. It is also possible to arrange the edge notch 170 in the transition region between the side surface of the semiconductor wafer 100 located at the front in the fracture direction 10 and the bottom side 102 of the semiconductor wafer 100, or to extend the edge notch 170 over the entire front side surface of the semiconductor wafer 100.

[0037] Additionally, an edge notch can also be arranged on the rear side surface of the semiconductor wafer 100 in the fracture direction 10, although this is not absolutely necessary. In any case, the fracture of the semiconductor wafer 100 occurs in the fracture direction 10 from the front side surface to the rear side surface of the semiconductor wafer 100.

[0038] To guide the fracture of the semiconductor wafer 100 at the fracture plane 20, the semiconductor wafer 100 also has a plurality of first upper depressions 200 on its upper side 101, which are arranged one behind the other along the fracture plane 20 in the fracture direction 10. The depressions 200 can also be referred to as skips.

[0039] The edge notches 170 and the first upper recesses 200 can be created, for example, by scribing, for example with a diamond scriber, or by means of a laser.

[0040] Preferably, an edge notch 170 and first upper depressions 200 are provided one after the other in the longitudinal direction 11 at each fracture plane 20.

[0041] Preferably, at each fracture plane 20, a first upper depression 200 is arranged between two laser diode structures that follow one another in the fracture direction 10, thus between two ribs 110 that follow one another in the fracture direction 10. Each first upper depression 200 is preferably arranged in the region between the rib 110 of the laser diode structure 141 arranged in front of the respective first upper depression 200 in the fracture direction 10, and the mesa trench 120 that lies between the two laser diode structures 141 adjacent to the respective first upper depression 200. Thus, each first upper depression 200 is arranged closer to the laser diode structure 141 that is closest in front of the respective first upper depression 200 in the fracture direction than to the laser diode structure 141 that is closest behind the respective first upper depression 200 in the fracture direction 10.Preferably, for each first upper depression 200, a rear distance 245 between the respective first upper depression 200 and the laser diode structure 141 closest to the respective first upper depression 200 in the fracture direction 10 is at least four times as large as a front distance 240 between the respective first upper depression 200 and the laser diode structure 141 closest to the respective first upper depression 200 in the fracture direction 10, and particularly preferably at least eight times as large. The front distance 240 between the resonator 142 of the laser diode structure 141 arranged in front of a first upper depression 200 and the respective first upper depression 200 can be, for example, approximately 20 µm. The rear distance 245 between a first upper depression 200 and the resonator 142 of the laser diode structure 141 closest in the fracture direction 10 behind this first upper depression 200 can be, for example, approximately 200 µm.

[0042] It is also possible to provide more than one recess 200 between two laser diode structures following one another in the fracture direction 10.

[0043] Each first upper depression 200 has a front boundary surface 210 in the fracture direction 10 and a rear boundary surface 220 in the fracture direction 10. The front boundary surface 210 and the rear boundary surface 220 of each first upper depression 200 are oriented parallel to the longitudinal direction 11 of the semiconductor wafer 100.

[0044] At its base, each first upper depression 200 has a bottom surface 230 which connects the front boundary surface 210 to the rear boundary surface 220 and is oriented substantially parallel to the top side 101 of the semiconductor wafer 100, i.e. parallel to the fracture direction 10 and the longitudinal direction 11.

[0045] For each first upper depression 200, the front boundary surface 210 forms a front angle 212 with the bottom surface 230. The front angle 212 is preferably between 75° and 95°, particularly preferably between 85° and 95°. This means that the front boundary surface 210, starting from the top side 101 of the semiconductor wafer 100, preferably extends substantially perpendicularly into the semiconductor wafer 100.

[0046] For each first upper depression 200, the rear boundary surface 220 in the fracture direction 10 forms a rear angle 221 with the bottom surface 230. The rear angle 221 is between 95° and 170°. This means that the rear boundary surface 220 is inclined toward the bottom surface 230 and toward the top side 101 of the semiconductor wafer 100. This results in each first upper depression 200 widening from its bottom surface 230 toward the top side 101 of the semiconductor wafer 100. The rear angle 221 for each first upper depression 200 preferably has a size between 100° and 160°, particularly preferably a size between 120° and 145°.

[0047] Each first upper depression 200 has a depth 211 in the growth direction 12. Preferably, the depth 211 of each first upper depression 200 is between 5 µm and 80 µm, particularly preferably between 15 µm and 70 µm, most preferably between 25 µm and 55 µm.

[0048] The bottom surface 230 of each first upper depression 200 has a length 231 in the fracture direction 10. Preferably, the length 231 for each first upper depression 200 is between 5 µm and 100 µm, particularly preferably between 15 µm and 80 µm, most preferably between 20 µm and 50 µm.

[0049] During the breaking of the semiconductor wafer 100 in the breaking direction 10 at one of the breaking planes 20, crystal defects 150 can form at the first upper depressions 200 and propagate within the semiconductor wafer 100. These crystal defects 150 can be, for example, step-like dislocations. The occurrence of such crystal defects 150 during the breaking of the semiconductor wafer 100 at one of the breaking planes 20 can result in reduced quality of the mirror surfaces formed by the breaking of the semiconductor wafer 100 at the breaking plane 20. It is particularly detrimental to the quality of the resulting mirror surfaces of the resonators 142 of the laser chips 140 formed by the breaking of the semiconductor wafer 100 if crystal defects 150 propagate within the semiconductor wafer 100 to an active region of one of the laser diode structures 141.

[0050] Crystal defects 150 arising during the fracture of the semiconductor wafer 100 in the fracture direction 100 at one of the fracture planes 20 are primarily formed at the rear boundary surfaces 220 of the first upper depressions 200 and continue from there in a direction perpendicular to the rear boundary surface 220. Since the rear boundary surfaces 220 of the first upper depressions 200 are inclined toward the upper side 101 of the semiconductor wafer 100 by the rear angle 221, which is greater than a right angle, the crystal defects 150 migrate from the rear boundary surfaces 220 of the first upper depressions 200 toward the underside 102 of the semiconductor wafer 100.This reduces the risk that crystal defects 150 formed on the rear boundary surface 220 of a first upper depression 200 will continue in the fracture direction 10 to the active region of the laser diode structure 141 following the respective first upper depression 200 in the fracture direction 10. This risk is further reduced by the rear distance 245, which is increased compared to the front distance 240, between the respective first upper depression 200 and the laser diode structure 141 closest to the respective first upper depression 200 in the fracture direction 10.

[0051] Preferably, all first upper depressions 200 arranged one behind the other in the fracture direction 10 of all fracture planes 20 arranged one behind the other in the longitudinal direction 11 of the semiconductor wafer 10 are formed as described. However, it is also possible for only a first part of the first upper depressions 200 to be formed and positioned as described, while a second part of the first upper depressions 200 is formed differently and / or positioned differently with respect to the front distance 240 and the rear distance 245.

[0052] Fig. 3 shows a schematic sectional side view of a part of the semiconductor wafer 100 according to an alternative embodiment. Also in the illustration of Fig. 3, the semiconductor wafer 100 is cut at one of the fracture planes 20. The embodiment of the Fig. 3 differs from the design of the Fig. 2 in that the first upper recesses 200 are replaced by second upper recesses 300.

[0053] The second upper depressions 300 are positioned like the first upper depressions 200. The second upper depressions 300 are formed like the first upper depressions 200, but in addition to the front boundary surface 210, the bottom surface 230, and the rear boundary surface 220, they have a shoulder 310 which adjoins the respective rear boundary surface 220 at the rear end of the respective second upper depression 300 in the breaking direction 10. The shoulder 310 of each second upper depression 300 has a shoulder surface 320 which is parallel to the top side 101 of the semiconductor wafer 100 and adjoins the respective rear boundary surface 220. This shoulder surface 320 has a length 321 in the breaking direction 10. Preferably, the length 321 of the shoulder surface 320 of the shoulder 310 of the second upper depressions 300 is between 5 µm and 100 µm, particularly preferably between 15 µm and 80 µm, most preferably between 20 µm and 50 µm.

[0054] When the semiconductor wafer 100 breaks in the fracture direction 10 at one of the fracture planes 20, crystal defects 150 can also arise on the shoulder surfaces 320 of the shoulders 310 of the second upper depressions 300, which, starting from the respective shoulder surface 320, continue into the semiconductor wafer 100 in a direction perpendicular to the respective shoulder surface 320. Since the shoulder surfaces 320 of the shoulders 310 of the second upper depressions 300 are oriented parallel to the upper side 101 of the semiconductor wafer 100, crystal defects 150 emanating from the shoulder surfaces 320 of the shoulders 310 of the second upper depressions 300 continue essentially counter to the growth direction 12 to the underside 102 of the semiconductor wafer 100. Thus, there is only a slight risk that crystal defects 150 emanating from the shoulder surfaces 320 can penetrate to active regions of the laser structures 141 of the semiconductor wafer 100.

[0055] In addition, crystal defects 150 emanating from the shoulder surfaces 320 of the shoulders 310 of the second upper depressions 300 can collide with crystal defects 150 emanating from the rear boundary surfaces 220 of the second upper depressions 300, which continue in a direction oriented perpendicular to the respective rear boundary surface 220, and thus intercept these crystal defects 150 emanating from the rear boundary surfaces 220. As a result, crystal defects 150 emanating from the shoulder surfaces 320 of the shoulders 310 of the second upper depressions 300 can reduce the risk of crystal defects 150 emanating from the rear boundary surfaces 220 of the second upper depressions 300 penetrating to active regions of the laser diode structures 141 of the semiconductor wafer 100.

[0056] In the schematic perspective representation of the Fig. 1 shows that on the underside 102 of the semiconductor wafer 100, in the region of each fracture plane 20, a lower trench 130 is formed, extending in the fracture direction 10 and arranged in the respective fracture plane 20. The lower trenches 130 can facilitate the breaking of the semiconductor wafer 100 at the fracture planes 10. The lower trenches 130 can be created, for example, by sawing, using a laser, or by wet or dry chemical etching. The lower trenches 130 are preferably created before the upper depressions 200, 300 and before the edge notches 170 are created. However, the lower trenches 130 can also be omitted.

[0057] Fig. 4 shows a schematic sectional side view of a portion of the semiconductor wafer 100 according to another alternative embodiment. Fig. In the embodiment shown in Figure 4, the semiconductor wafer 100 does not have any lower trenches 130 aligned with the fracture planes 20 on its underside 102. Instead, lower depressions 400 are provided on the underside 102 of the semiconductor wafer 100, each aligned with the fracture planes 20 and arranged one behind the other in the fracture direction 10.

[0058] The lower recesses 400 are in Fig. 4, the semiconductor wafer 100 is arranged and formed mirror-symmetrically to the second upper depressions 300 arranged on the upper side 101 of the semiconductor wafer 100. If the semiconductor wafer 100 has the first upper depressions 200 of the Fig. 2, the lower recesses 400 can be formed as a mirror image of the first upper recesses 200. However, it is also possible to provide the first upper recesses 200 on the top side 101 of the semiconductor wafer 100, and to form the lower recesses 400 on the underside 102 of the semiconductor wafer 100 like the second upper recesses 300. The reverse case is also possible, of course.

[0059] In the presentation of the Fig. 4, the lower depressions 400 are arranged exactly below the second upper depressions 300, opposite to the growth direction 12. However, it is also possible to arrange the second upper depressions 300 and the lower depressions 400 offset from one another in the fracture direction 10. For example, the lower depressions 400 can each be arranged behind the associated second upper depressions 300 in the fracture direction 10.

[0060] When the semiconductor wafer 100 breaks in the fracture direction 10 at one of the fracture planes 20, crystal defects 150 can also form on the rear boundary surfaces of the lower depressions 400. These crystal defects 150 formed on the rear boundary surfaces of the lower depressions 400 continue in the semiconductor wafer 100 in a direction perpendicular to the rear boundary surface of the respective lower depression 400 and thus run in the direction of the upper side 101 of the semiconductor wafer 100. In doing so, they can collide with crystal defects 150 emanating from rear boundary surfaces 220 of the opposite upper depressions 300. In this case, the colliding crystal defects 150 can intercept each other and thus prevent further continuation of the crystal defects 150 in the semiconductor wafer 100.This reduces the risk that crystal defects 150 emanating from the depressions 300, 400 penetrate to active regions of the laser diode structures 141 of the semiconductor wafer 100.

[0061] The invention has been illustrated and described in more detail using the preferred embodiments. However, the invention is not limited to the disclosed examples. Rather, other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention. List of reference symbols 10 Fracture direction 11 Longitudinal direction 12 Growth direction 20 fracture plane 30 additional fracture levels 100 semiconductor wafers 101 Top 102 subpage 110 rib 120 Mesa Trench 130 lower ditch 140 laser chips 141 Laser diode structure 142 Resonator 150 Crystal disturbance 160 front edge 170 edge notch 200 first upper depressions 210 front boundary surface 211 depth 212 front angle 220 rear boundary surface 221 rear angle 230 floor space 231 length 240 front distance 245 rear distance 300 second upper depressions 310 paragraph 320 sales area 321 length 400 lower recess

Claims

[1] A method for manufacturing a laser chip (140) comprising the following steps: - Providing a semiconductor wafer (100) having a top side (101) and a bottom side (102), wherein the semiconductor wafer (100) has a plurality of integrated laser diode structures (141) arranged one behind the other along a predetermined fracture direction (10); - creating a plurality of depressions (200, 300) arranged one behind the other along the fracture direction (10) on the upper side (101) of the semiconductor wafer (100), wherein one of the depressions (200, 300) is arranged between each two adjacent laser diode structures (141), wherein each of the recesses (200, 300) has a front boundary surface (210) and a rear boundary surface (220) successively in the fracture direction (10), wherein in at least one of the recesses (200, 300) the rear boundary surface (220) is inclined relative to the upper side (101) of the semiconductor wafer (100) by an angle (221) between 95° and 170°, wherein at least one of the depressions (200, 300) is arranged closer to a laser diode structure (141) located closest in front of the depression (200, 300) in the fracture direction (10) than to a laser diode structure (141) located closest behind the depression (200, 300) in the fracture direction (10), wherein the distance (245) between the depression (200, 300) and the laser diode structure (141) closest to the depression (200, 300) in the fracture direction (10) is at least four times as large as the distance (240) between the depression (200, 300) and the laser diode structure (141) closest to the depression (200, 300) in the fracture direction (10), preferably at least eight times as large; - breaking the semiconductor wafer (100) in the breaking direction (10) at a breaking plane (20) oriented perpendicular to the upper side (101) of the semiconductor wafer (100) and passing through the recesses (200, 300). [2] Method according to one of the preceding claims, wherein each of the laser diode structures (141) has a resonator (142) oriented perpendicular to the fracture direction (10). [3] Method according to one of the preceding claims, wherein the recesses (200, 300) are created by scribing or by means of a laser. [4] A method according to any one of the preceding claims, wherein the method comprises the following further step: - Applying an edge notch (170) arranged in the fracture plane (20) to an edge (160) of the semiconductor wafer (100) lying at the front in the fracture direction (10). [5] A method according to any one of the preceding claims, wherein the method comprises the following further step: - Creating a trench (130) running in the fracture direction (10) and arranged in the fracture plane (20) on the underside (102) of the semiconductor wafer (100). [6] The method according to claim 5, wherein the trench (130) is created by sawing, by means of a laser or by an etching process. [7] A method according to any one of claims 1 to 4, wherein the method comprises the following further step: - Creating a plurality of underside depressions (400) arranged one behind the other in the fracture plane (20) and along the fracture direction (10) on the underside (102) of the semiconductor wafer (100). [8] Method according to claim 7, wherein the underside recesses (400) on the underside (102) of the semiconductor wafer (100) are formed in a mirror image to the recesses (200, 300) on the top side (101) of the semiconductor wafer (100). [9] Method according to one of the preceding claims, wherein in at least one of the depressions (200, 300) on the upper side (101) of the semiconductor wafer (100), the rear boundary surface (220) is inclined relative to the upper side (101) of the semiconductor wafer (100) by an angle (221) between 100° and 160°, preferably by an angle (221) between 120° and 145°. [10] Method according to one of the preceding claims, wherein at least one of the depressions (200, 300) on the upper side (101) of the semiconductor wafer (100) has a depth (211) in the direction (12) perpendicular to the upper side (101) of the semiconductor wafer (100) which lies between 5 µm and 80 µm, preferably between 15 µm and 70 µm, particularly preferably between 25 µm and 55 µm. [11] Method according to one of the preceding claims, wherein in at least one of the depressions (200, 300) on the upper side (101) of the semiconductor wafer (100), the front boundary surface (210) is inclined relative to the upper side (101) of the semiconductor wafer (100) by an angle (212) between 75° and 95°, preferably by an angle (212) between 85° and 95°. [12] Method according to one of the preceding claims, wherein at least one of the depressions (200, 300) on the upper side (101) of the semiconductor wafer (100) has at its base in the fracture direction (10) a length (231) which is between 5 µm and 100 µm, preferably between 15 µm and 80 µm, particularly preferably between 20 µm and 50 µm. [13] Method according to one of the preceding claims, wherein at least one of the depressions (300) on the upper side (101) of the semiconductor wafer (100) has a shoulder (310) adjoining the rear boundary surface (220), wherein the shoulder (310) has a shoulder surface (320) parallel to the upper side (101) of the semiconductor wafer (100) and adjoining the rear boundary surface (220). [14] Method according to claim 13, wherein the shoulder surface (320) in the fracture direction (10) has a length (321) between 5 µm and 100 µm, preferably a length (321) between 15 µm and 80 µm, particularly preferably a length (321) between 20 µm and 50 µm.

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