LASER DEVICE AND METHOD

Abstract

The invention relates to an optoelectronic laser device comprising: a semiconductor layer stack having an active zone arranged between a first layer of a first conductivity type and a second layer of a second conductivity type, at least one structure designed to constrict current in the active zone to generate laser radiation, and a first front side extending from a first top side in the direction of a first bottom side opposite the first top side and having an exit window for the laser radiation generated in the active zone;a carrier substrate with an electrical via extending from a second top side to an opposite second bottom side, and a second front side extending from the second bottom side toward the second top side, the second front side having a first section adjoining the second top side and a second section set back from the first section; and an electrical contact layer arranged on the first bottom side and configured to be arranged on a contact element and electrically connected to the first layer. The first top side and the second bottom side are arranged adjacent to one another in contact, and the electrical via is electrically connected to the second layer.

Description

[0001] The present invention relates to a laser device and a method for producing a laser device. BACKGROUND

[0002] Laser diodes, and especially high-power laser diodes, require good heat dissipation to achieve their full optical performance. Until now, laser diodes have usually been mounted with their growth substrate side facing down on a target substrate, or they have been mounted with the side opposite the growth substrate facing down on a heat sink with high thermal conductivity. However, since both cases result in a long heat path between the laser diode and the target substrate (through the entire growth substrate or through passivation layers on the surface of the laser diode and the entire heat sink), and since the output power of laser diodes is constantly increasing, there is a need to provide an optoelectronic laser device with reduced thermal resistance, as well as a method for manufacturing such an optoelectronic laser device, which counteracts at least one of the aforementioned problems. SUMMARY OF THE INVENTION

[0003] This need is addressed by the subject matter of the independent patent claims. Further developments and embodiments of the proposed principle are specified in the subclaims.

[0004] The core idea of ​​the invention is to provide a method that makes it possible to thin an edge-emitting laser diode or the semiconductor body of the laser diode at the wafer level from the growth substrate side in such a way that the laser diode can be applied to a target substrate essentially directly, without additional passivation layers, etc., and with the shortest possible heat path. For this purpose, during wafer-level production, a carrier substrate is applied to a side opposite the growth substrate. This carrier substrate fixes the semiconductor body and enables the semiconductor body to be thinned from the growth substrate side.Subsequently separated laser devices, which consist of the thinned semiconductor body and a portion of the carrier substrate, have only a thin residual region of the semiconductor body between a mounting side and the active zone, in which the heat is generated during the generation of laser radiation, so that the heat path between the semiconductor body and the target substrate on which the laser device is mounted with the mounting side is as short as possible. The carrier substrate remains on the semiconductor body in the separated laser device and, due to the preceding manufacturing steps, has a corresponding characteristic shape to provide an exposed light exit window for the laser radiation generated in the semiconductor body and to prevent beam clipping of the laser radiation emitted from the light exit window.Compared to existing processes for manufacturing edge-emitting lasers, the proposed process is not limited to a minimum thickness of the semiconductor body to enable stable production. However, attaching the semiconductor body to a secondary substrate prior to singulating individual laser devices allows for further processing of the semiconductor body beyond the limits of the state of the art.

[0005] Among other things, the invention offers a solution to the requirement for a short thermal path and correspondingly improved thermal performance. Furthermore, the proposed laser device can reduce electrical losses within the laser device and correspondingly improve the system performance of an arrangement comprising the proposed laser device. Furthermore, the proposed method enables the use of mass production processes to ensure reduced costs for manufacturing the proposed laser device.

[0006] According to a first aspect, an optoelectronic laser device is specified. The optoelectronic laser device comprises a semiconductor layer stack with an active zone arranged between a first layer of a first conductivity type and a second layer of a second conductivity type, as well as at least one structure designed to constrict current in the active zone to generate laser radiation. Furthermore, the semiconductor layer stack comprises a first front side extending from a first top side toward a first bottom side opposite the first top side and having an exit window for the laser radiation generated in the active zone. The semiconductor layer stack can be designed, in particular, in the form of an edge-emitting laser diode, and the exit window can be referred to, in particular, as a laser facet and adjoin the active zone at the first front side.

[0007] The optoelectronic laser device further comprises a carrier substrate with an electrical via extending from a second upper side to an opposite second lower side, and a second front side extending from the second lower side toward the second upper side. The second front side has a first section adjoining the second upper side and a second section set back from the first section, so that the second front side is configured, at least in some regions, in particular in a stepped manner.

[0008] Furthermore, an electrical contact layer is arranged on the first underside, which is designed to be arranged on a contact element and is electrically connected to the first layer. In particular, the optoelectronic laser device can be subjected to a first electrical potential via the electrical contact layer to generate laser radiation.

[0009] The semiconductor layer stack and the carrier substrate are arranged relative to one another or adjacent to one another such that the first top side and the second bottom side touch each other. Furthermore, the semiconductor layer stack and the carrier substrate are arranged or configured such that the electrical via is electrically connected to the second layer. In particular, the optoelectronic laser device can be subjected to a second electrical potential via the electrical via to generate laser radiation.

[0010] The thermal performance of the proposed laser device can be improved in particular by applying the semiconductor body of the laser device with its growth substrate side directly to a target substrate. However, in contrast to known solutions, the thickness between the electrical contact layer and the active zone for generating laser radiation is significantly reduced. This is achieved by thinning the semiconductor body, which in turn is only made possible by using the carrier substrate, which is applied to the semiconductor layer sequence before singulating individual laser devices at the wafer level. Furthermore, parasitic electrical path(s) can be reduced by thinning the semiconductor body and removing a growth substrate and applying the electrical contact layer.Reducing the thermal path(s) and series resistance leads to a significant improvement in the efficiency of the laser device. Furthermore, wafer-level processing enables a cost-effective approach to laser device manufacturing.

[0011] With the help of etched facet technology to create the exit window for the laser radiation generated in the active zone and with the help of a pre-structured carrier substrate comprising an electrical via(s), e.g., SiC with vias or Si with a through-silicon via (TSV), a singulated chip-scale package (CSP) can be achieved for applications requiring a laser device that emits laser radiation laterally. The etched facet technology for creating the exit window and the pre-structured carrier substrate enable the creation of the exit window at the wafer level and the singulation of the laser device without damaging the created exit window.

[0012] According to at least one embodiment, the first front side has a third section adjoining the first underside and a fourth section set back from the third section, so that the first front side is also designed, at least in some regions, to be stepped. In particular, the fourth section of the first front side of the semiconductor layer stack, which is set back from the third section, has the exit window. In particular, the fourth section can extend through the second layer, the active zone, and into the first view, whereas the third section can extend only through the first layer of the semiconductor layer stack.The step shape can in particular result from two separate structuring steps, wherein a first structuring step is provided to produce the exit window so that the fourth section of the first front side is created, and a second structuring step serves to separate the laser device so that the third section of the first front side is created.

[0013] According to at least one embodiment, the second section and the first front side, and in particular the fourth section of the first front side, lie substantially in the same plane. In particular, a region of the first front side that has the exit window and the second section of the second front side of the carrier substrate, which is set back relative to the first section, can lie substantially in the same plane.

[0014] According to at least one embodiment, the first section of the second front side of the carrier substrate and the third section of the first front side lie substantially in the same plane. In particular, a region of the first front side that does not have the exit window and the first section of the second front side of the carrier substrate can lie substantially in the same plane.

[0015] According to at least one embodiment, the active zone is arranged between two waveguide layers. In particular, the active zone can be arranged between two layers with a lower refractive index than the material of the active zone, so that an optical wave generated in the active zone is guided along the active zone.

[0016] Due to the differences in refractive index and the associated total reflection, the two waveguide layers and the active zone can together form a waveguide along which the optical wave propagates before it can be coupled out via the exit window adjacent to the active zone.

[0017] According to at least one embodiment, the at least one structure configured for current constriction in the active zone for generating laser radiation is formed, for example, by a strip contact (gain guide) on the second layer or by structuring (index guide, by ridge etching, or lateral intermixing of the second layer). In particular, the structure for current constriction can be configured such that current injection occurs only in a narrow region of the active zone, adjacent to the exit window, so that an optical wave forms in this region, which propagates along the active zone and in particular along the narrow region.For this purpose, a highly reflective mirror can also be provided on a first rear side of the semiconductor layer stack opposite the first front side, and in particular directly opposite the exit window. This mirror reflects an optical wave propagating between the exit window and the highly reflective mirror toward the exit window. Furthermore, the exit window can be partially reflective, as is already known from commercial edge-emitting laser diodes. The aforementioned structure can provide a so-called laser channel in the laser device.

[0018] According to at least one embodiment, the fourth section is formed by a first recess in the semiconductor layer stack, which extends from the first upper side toward the first lower side. Additionally or alternatively, the second section can be formed by a second recess in the carrier substrate, which extends from the second lower side toward the second upper side.

[0019] The first recess can extend over the entire width of the first top side when viewed in plan view of the first top side, or can be formed, for example, by a pocket in the semiconductor layer stack which, when viewed in plan view of the first top side, does not extend over the entire width of the first top side, but in particular over at most 200 µm of the width of the first top side. The first front side can accordingly have a region in the form of the fourth section which, when viewed in plan view of the first top side, extends over the entire width of the first top side, or which, when viewed in plan view of the first top side, does not extend over the entire width of the first top side.In the latter case, the first front side in particular may have a region in the form of the third section which, viewed in plan view of the first front side, borders the fourth region on three sides and is correspondingly U-shaped viewed in plan view of the first front side and borders the fourth region on three sides.

[0020] Alternatively or additionally, the second recess can extend over the entire width of the second underside when viewed in plan view of the second underside, or it can be formed, for example, by a pocket in the carrier substrate which, when viewed in plan view of the second underside, does not extend over the entire width of the second underside, but in particular over at most 200 µm of the width of the second underside. The second front side can accordingly have a region in the form of the second section which, when viewed in plan view of the second underside, extends over the entire width of the second underside, or which, when viewed in plan view of the second underside, does not extend over the entire width of the second underside.In the latter case, the second front side in particular may have a region in the form of the first section which, viewed in plan view of the second front side, borders the second region on three sides and is correspondingly U-shaped viewed in plan view of the second front side and delimits the second region on three sides.

[0021] According to at least one embodiment, the semiconductor layer stack has a thickness of at most 50 µm, in particular at most 30 µm, or at most 15 µm. Thanks to such a small thickness, in combination with the electrical contact layer arranged on the first underside, which is designed to be arranged on a contact element, a heat path between the active zone, in which heat is generated during the generation of laser radiation, and a target substrate can be as small as possible, thus increasing the thermal performance of the laser device.

[0022] According to at least one embodiment, the active zone is arranged at a closer distance to the first top side than to the first bottom side. In particular, this can achieve the effect that the remaining first layer, together with the electrical contact layer, acts as a type of submount, thus preventing beam clipping of laser radiation emitted from the exit window. However, the position of the active zone relative to the first bottom side or the first top side can also be varied, in particular by varying the degree of thinning of the semiconductor layer stack.

[0023] According to at least one embodiment, the fourth section is set back from the third section by a maximum of 100 µm, and in particular by at least 10 µm. Additionally or alternatively, the second section can be set back from the first section by a maximum of 100 µm, and in particular by at least 10 µm. The depth of the second or fourth section relative to the first or third section can in particular be selected to be large enough to prevent damage to the exit window during singulation of the laser device, while at the same time being selected to be small enough to prevent beam clipping of laser radiation emitted from the exit window.

[0024] According to at least one embodiment, the semiconductor layer stack further comprises a first rear side opposite the first front side, which extends from the first top side toward the first bottom side. The first rear side can be configured to correspond to the first front side and, for example, can comprise a fifth section adjoining the first bottom side and a sixth section set back from the fifth section.

[0025] According to at least one embodiment, the carrier substrate further comprises a second rear side opposite the second front side, which extends from the second upper side toward the second lower side. The second rear side can be configured to correspond to the second front side and, for example, have a seventh section adjoining the second upper side and an eighth section set back from the seventh section.

[0026] According to at least one embodiment, the semiconductor layer stack has a plurality of structures designed to constrict current in the active zone for generating laser radiation. At the same time, the semiconductor layer stack has, on its first front side, a plurality of exit windows arranged downstream of the active zone in a region of a respective current constriction. Each structure designed to constrict current in the active zone for generating laser radiation, in conjunction with an exit window, can form, in particular, a laser channel in the semiconductor layer stack. Accordingly, the laser device can have not only one laser channel, but also a plurality of laser channels formed adjacent to one another in the laser device in the semiconductor layer stack.

[0027] The exit windows can be formed in a continuous first front side, in a common section of the first front side, or in separate sections of the first front side. For example, the exit windows can each be exposed through a separate pocket in the semiconductor layer stack, a first number of exit windows can be exposed through a first pocket and another number of exit windows can be exposed through a second pocket, or all exit windows can be exposed through a common pocket or recess.

[0028] The structures designed to constrict current in the active zone for generating laser radiation can, for example, be formed by individual strip contacts on the second layer or by structuring the second layer. Furthermore, the electrical contact layer arranged on the first underside can be formed by several separate contact layers to enable the individual laser channels to be controlled separately, or it can be formed by a common contact layer that contacts all laser channels simultaneously.

[0029] According to at least one embodiment, the electrical via extends substantially centrally through the carrier substrate and accordingly contacts substantially centrally the second layer or the structure designed for current constriction in the active zone for generating laser radiation. The via can be formed, for example, by a TSV. However, the via can also be formed by an opening through the carrier substrate, the inner wall of which is coated with an electrically conductive material. For example, the electrical via can also be formed in an edge region of the carrier substrate and, for example, be formed only by a cylinder segment that extends from the second top side to the second bottom side.This can occur, for example, because before a separation of several laser devices, an electrical via for several adjacent laser devices may have been provided through the carrier substrate, which is separated during the separation.

[0030] According to at least one embodiment, the semiconductor layer stack comprises gallium nitride (GaN) or gallium arsenide (GaAs) or consists largely of GaN or GaAs. In particular, the semiconductor layer stack may comprise indium aluminum gallium arsenide (InAlGaAs) or indium gallium nitride (InGaN) substrate. Other possible materials for the semiconductor layer stack may be aluminum nitride or gallium arsenide.

[0031] According to at least one embodiment, the carrier substrate comprises a ceramic material and / or a semiconductor material such as Si or SiC.

[0032] Furthermore, a method for producing a laser device is specified. In particular, a laser device described here can be produced by means of the method. This means that all features disclosed for the laser device are also disclosed for the method, and vice versa.

[0033] A method for manufacturing a laser device according to another aspect comprises the following steps: Providing a semiconductor layer stack (with an active zone arranged between a first layer of a first conductivity type and a second layer of a second conductivity type, and at least one structure designed to constrict current in the active zone to generate laser radiation; Creating at least one first recess in the semiconductor layer stack such that a fourth section of a first front side of the semiconductor layer stack is exposed, which section extends from a first top side of the semiconductor layer stack through the second layer, the active zone and into the first layer, and which exposes an exit window for the laser radiation generated in the active zone; Providing a carrier substrate with an electrical via extending from a second top side to an opposite second bottom side, and at least one second recess extending from the second bottom side toward the second top side and exposing a second portion of a second front side; Applying the first top side to the second bottom side such that the first top side and the second bottom side are arranged touching one another, the electrical via is in electrical connection with the second layer, and the first and second recesses are substantially opposite one another; Thinning the semiconductor layer stack such that a first bottom side of the semiconductor layer stack opposite the first top side is exposed; and Applying an electrical contact layer on the first underside, which is in electrical connection with the first layer and which is designed to be arranged on a contact element.

[0034] According to at least one embodiment, the first and the second recess are substantially identically dimensioned, and the step of applying the first upper side to the second lower side is carried out in such a way that the first and the second recess are substantially congruent with each other.

[0035] According to at least one embodiment, the step of thinning the semiconductor layer stack is carried out in such a way, and in particular to such a depth, that the at least one first recess is opened from a side opposite the first top side. Accordingly, the step of thinning the semiconductor layer stack can be carried out in such a way that any material of the first layer between the first bottom side and the first recess is removed.

[0036] According to at least one embodiment, the step of thinning the semiconductor layer stack is carried out such that the remaining semiconductor layer stack has a thickness of at most 50 µm, in particular at most 30 µm, or at most 15 µm.

[0037] According to at least one embodiment, the method further comprises severing at least the carrier substrate in the region of the at least one second recess, wherein the severing exposes a first portion of the second front side, which extends from the second top side toward the second bottom side, and wherein the second portion is set back from the first portion. The severing step can, in particular, be a singulation step between a plurality of laser devices arranged side by side.

[0038] According to at least one embodiment, the step of severing comprises severing the semiconductor layer stack in the region of the at least one first recess, wherein severing the semiconductor layer stack exposes a third section of the first front side, which extends from the first underside in the direction of the first top side, and wherein the fourth section is set back from the third section.

[0039] According to at least one embodiment, the step of applying the first upper side to the second lower side is carried out in such a way that the at least one first recess and the at least one second recess are substantially congruent with one another, in particular in such a way that the second section and the fourth section lie substantially in the same plane.

[0040] The first recess can extend over the entire width of the first top side, in particular in the form of a trench, as seen in a plan view of the first top side, or can be formed, for example, by one or more pockets in the semiconductor layer stack, which, as seen in a plan view of the first top side, do not extend over the entire width of the first top side, but rather in particular over at most 200 µm of the width of the first top side.

[0041] Alternatively or additionally, the second recess can extend over the entire width of the second underside when viewed in plan view of the second underside, in particular in the form of a trench, or it can be formed, for example, by one or more pockets in the carrier substrate which, when viewed in plan view of the second underside, do not extend over the entire width of the second underside, but in particular each over at most 200 µm of the width of the second underside.

[0042] According to at least one embodiment, the step of providing the semiconductor layer stack comprises providing the semiconductor layer stack with a plurality of structures configured to constrict current in the active zone for generating laser radiation. Furthermore, the method comprises creating a plurality of first recesses in the semiconductor layer stack such that a plurality of fourth sections of first front sides of the semiconductor layer stack are exposed, each of which extends from a first top side of the semiconductor layer stack through the second layer, the active zone, and into the first layer, and each of which exposes at least one exit window for the laser radiation generated in the active zone.Furthermore, the step of providing the carrier substrate comprises providing the carrier substrate with a plurality of second recesses extending from the second bottom side toward the second top side and exposing a plurality of second portions of second front sides, wherein the carrier substrate has a plurality of electrical vias extending from the second top side to the second bottom side. In particular, the method can be used to simultaneously manufacture multiple laser devices and / or laser devices with more than one laser channel at the wafer level.

[0043] According to at least one embodiment, a plurality of laser devices are separated by means of the severing step, each of which comprises at least one of the plurality of current constriction structures and one of the plurality of exit windows and each of which comprises at least one electrical via that is in electrical connection to a partial region of the second layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Further aspects and embodiments according to the proposed principle will become apparent with reference to the various embodiments and examples which will be described in detail in conjunction with the accompanying drawings. Fig. 1A to 1D show steps of a method for manufacturing a laser device according to the proposed principle; Fig. 2A to 2C each show a plan view of a bottom side of a laser device according to the proposed principle; Fig. 3 shows a sectional view of a laser device according to the proposed principle mounted on a target substrate; Fig. 4A to 4D show steps of another method for manufacturing a laser device according to the proposed principle; Fig. 5 shows a sectional view of another embodiment of a laser device according to the proposed principle mounted on a target substrate; Fig. 6A to 6E show steps of another method for manufacturing a laser device according to the proposed principle and detailed views of the semiconductor layer stack; Fig. 7A to 7G show a step of another method for manufacturing a laser device according to the proposed principle and detailed views of the carrier substrate; Fig. 8A to 8D show steps of another method for manufacturing a laser device according to the proposed principle and detailed views of the semiconductor layer stack; Fig. 9A to 9E show a step of another method for manufacturing a laser device according to the proposed principle as well as detailed views of the carrier substrate. DETAILED DESCRIPTION

[0045] The following embodiments and examples illustrate various aspects and their combinations according to the proposed principle. The embodiments and examples are not always to scale. Likewise, various elements may be enlarged or reduced in size to emphasize individual aspects. It goes without saying that the individual aspects and features of the embodiments and examples shown in the figures can be readily combined with one another without compromising the inventive principle. Some aspects have a regular structure or shape. It should be noted that minor deviations from the ideal shape may occur in practice without, however, contradicting the inventive idea.

[0046] Furthermore, the individual figures, features, and aspects are not necessarily depicted in the correct size, nor are the proportions between the individual elements necessarily accurate. Some aspects and features are emphasized by being enlarged. However, terms such as "top," "above," "below," "below," "larger," "smaller," and the like are correctly depicted in relation to the elements in the figures. This makes it possible to infer such relationships between the elements from the illustrations.

[0047] The Fig. Figures 1A to 1D show steps of a method for manufacturing a laser device 1 according to the proposed principle. The left part of the figures shows a schematic sequence at the wafer level, while the right part of the figures shows a sectional view of the intermediate products of the method.

[0048] In a first step, a semiconductor layer stack 2 is provided with an active zone arranged between a first layer of a first conductivity type and a second layer of a second conductivity type. In addition to the layer sequence not shown in detail, the semiconductor layer stack 2 has a plurality of structures designed to constrict current in the active zone to generate laser radiation.The step further comprises creating first recesses 15a in the semiconductor layer stack 2 such that a fourth section 13d of first front sides of the semiconductor layer stack 2 of laser devices formed later and an opposite sixth section 13f of first rear sides of the semiconductor layer stack 2 of laser devices formed later are exposed, which extend from a first top side 8a of the semiconductor layer stack 2 through the second layer, the active zone, and into the first layer. Furthermore, the first recesses 15a each expose at least one exit window (not shown in detail here) for laser radiation generated in the active zone, which exit windows are each arranged in the fourth sections. The step of creating the first recesses can in particular comprise a process by means of which the exit windows are created or etched free in the form of laser facets.

[0049] In a further step, as in Fig. 1B, a carrier substrate 11 is provided and arranged on the semiconductor layer stack 2. The carrier substrate 11 has electrical vias 12 that extend from a second top side 8b to an opposite second bottom side 9b. Furthermore, the carrier substrate 11 has second cutouts 15b that extend from the second bottom side 9b toward the second top side 8b and that each expose a second section 13b of a second front side 7b of the carrier substrate 11 of laser devices formed later, as well as an eighth section 13h of a second rear side 16b of the carrier substrate 11 of laser devices formed later.

[0050] The carrier substrate 11 is arranged on the semiconductor layer stack 2 in such a way that the first top side 8a and the second bottom side 9b are arranged adjacent to each other in contact, that the electrical vias 12 are electrically connected to the remaining regions of the second layer 5, and that the first and second recesses 15a, 15b are each substantially congruent with each other. This creates cavities between the carrier substrate 11 and the semiconductor layer stack 2, each formed by a first and a second recess 15a, 15b.

[0051] Optionally, the carrier substrate 11 can have separation marks 19 in the form of trenches on its second upper side 8b, which facilitate later separation of several laser devices from the wafer structure.

[0052] In a further step, as in Fig. 1C, the semiconductor layer stack 2 is thinned from a side opposite the carrier substrate 11, such that a first bottom side 9a of the semiconductor layer stack 2, opposite the first top side 8a, is exposed. The thinning has the effect that unnecessary material of the first layer can be removed in order to improve heat dissipation of the laser devices formed later through the first layer. After the thinning, electrical contact layers 14 are also applied to the exposed first bottom side 9a, which are in electrical connection with the first layer and are designed to be arranged at a later time on a contact element, for example a contact element on a target substrate for the laser devices.

[0053] In a subsequent step, as in Fig. 1D, individual laser devices 1 are separated from the wafer structure. In particular, laser devices 1 can be separated by the separation as shown in the right part of the Fig. 1D. The step of singulation can be carried out in particular along the separation markings 19 and can comprise severing the carrier substrate 11 and the semiconductor layer stack 2 in the region of the first and second recesses 15a, 15b.

[0054] The laser devices 1 each comprise a portion of the semiconductor layer stack 2, each having at least one structure configured to constrict current in the active zone 3 to generate laser radiation L. In particular, each laser device 1 has at least one laser channel extending along the active zone between an exit window 10 and a mirror on the opposite first rear side 16a, in particular in the sixth section 13f of the first rear side 16a. Laser radiation L generated in the active zone can be emitted via the exit window 10.

[0055] Due to the creation of the first recesses 15a and the subsequent singulation, the semiconductor layer stack 2 of the laser devices 1 each has a first front side 7a, which is composed of a third and a fourth section 13c, 13d, wherein the fourth section 13d is set back from the third section 13c. Likewise, the semiconductor layer stack 2 of the laser devices 1 each has a first rear side 16a, which is composed of a fifth and a sixth section 13e, 13f, wherein the sixth section 13f is set back from the fifth section 13e.

[0056] Due to the creation of the second recesses 15b and the subsequent singulation, the carrier substrate 11 of each laser device 1 is also designed such that the carrier substrate 11 of the laser devices 1 each has a second front side 7b, which is composed of a first and a second section 13a, 13b, wherein the second section 13b is set back from the first section 13a. Likewise, the carrier substrate of the laser devices 1 each has a second rear side 16b, which is composed of a seventh and an eighth section 13g, 13h, wherein the eighth section 13h is set back from the seventh section 13g.

[0057] Each laser channel is electrically connected to at least one electrical via 12 and at least one electrical contact layer 14 in order to be able to operate the laser channel in the desired manner.

[0058] The fact that the fourth section 13d is set back from the third section 13c is due in particular to the fact that separating the laser devices 1 in the immediate vicinity of the exit windows 10 could damage the exit windows 10, so that the separating step takes place at a distance from the fourth section 13d. In order to prevent beam clipping of a laser radiation L emitted from the recessed exit windows 10 by the carrier substrate 11, the second recesses 15b were introduced into the carrier substrate 11, so that a recessed section or a step is also produced for these in the region of the second front side 7b. The step formed in the two rear sides 16a, 16b, in particular in the semiconductor layer stack 2, can be provided for similar considerations.In particular, a reflective surface formed at the exit window 10 and in the sixth section is intended to be protected by the step during the separation of the laser devices 1. Furthermore, the present structure can be created due to the manufacturing and separation of the recesses on both the front and back sides.

[0059] The Fig. 2A to 2C each show a plan view of a first underside 9a of a laser device 1 according to the proposed principle. In particular, the figures are intended to show that a laser device 1 can have several laser channels arranged side by side, each with a respective exit window. The laser channels can be controlled by means of a common electrical contact layer 14 ( Fig. 2C), or can be controlled separately by means of several electrical contact layers 14 arranged on the first underside 9a ( Fig. 2B).

[0060] Fig. Figure 3 shows a sectional view of a laser device 1 according to the proposed principle, which is mounted on a target substrate 17. The laser device 1, in particular the electrical via 12, is also electrically connected to its second upper side 8b via a wire contact 18.

[0061] The laser device 1 is mounted on the target substrate 17 with the thinned semiconductor layer stack 2 facing downwards.

[0062] This enables effective heat dissipation of the laser device 1 through the first layer 4. In particular, the semiconductor layer stack 2 is thinned to a thickness t1 of at most 50 µm, in particular at most 30 µm, or at most 15 µm, while the carrier substrate 11 can have a thickness t2 of, for example, 80 µm to 200 µm for stabilization during the manufacture of the laser device.

[0063] The Fig. 4A to 4D show, as in Fig. 1A to 1D show steps of a further method for manufacturing a laser device according to the proposed principle. The only difference is the Fig. 4C, namely, that the thinning of the semiconductor layer stack 2 is carried out to a depth such that the first recesses 15a are reached. Accordingly, the cavities between the semiconductor layer stack 2 and the carrier substrate 11 are opened already at the time of thinning and not only at the time of singulation. This has the consequence that the first front sides 7a, at least in the region of the exit windows 10, do not have the Fig. 1C shown level.

[0064] By means of such a thinning, the semiconductor layer stack 2 can be made even thinner in order to provide even better heat dissipation of the laser device 1. A Fig. The laser device shown in Figure 4C is shown in a sectional view in Fig. 5, which is mounted on a target substrate 17.

[0065] Fig. 6A to 6E show two plan views of only the semiconductor stack 2 during steps of a method for producing a laser device 1 according to the proposed principle, as well as detailed views and sectional views of the semiconductor layer stack 2 of a resulting laser device 1.

[0066] In particular, it is shown which shape the first recesses 15a can have and how they can be distributed in the semiconductor layer stack 2. The shown shape in the form of pockets or arrangement in the form of a matrix arrangement is, however, to be understood as an example and can be varied. For example, differently shaped pockets in the form of circles, ovals, hexagons, octagons, etc. would also be conceivable. In particular, it can be seen that the structure 6 for current constriction is interrupted by the pockets and that exit windows 10 or opposite reflective end surfaces are exposed through the pockets. The pockets can be formed with a desired width b1 and a desired length 11 depending on requirements.

[0067] In Fig. 6A also shows that a later lighting device 1 can comprise only one structure 6 for current constriction and accordingly has only one laser channel, or that a later lighting device 1 can comprise several structures 6 for current constriction and accordingly has several laser channels. The pockets can in particular be designed such that they do not extend over the entire width of the first upper side 8a of a later laser device, but only over a central area. Viewed from above, as also in the detailed view in Fig. 6C, an H-shaped first upper side 8a can result. The length 11 of the pockets can, in particular, determine the depth by which the fourth section 13d is set back from a later-created third section 13c of the first front side 7a.

[0068] Fig. 6B shows the dividing lines 20 along which the laser devices 1 are separated, resulting in the third sections 13c of the first front sides 7a and the fifth sections 13e of the first rear sides 16a. Due to the matrix arrangement of the pockets, dividing lines 20 are formed in two mutually perpendicular directions x, y, so that a plurality of laser devices 1 arranged in a matrix can be obtained.

[0069] Such a resulting laser device or its semiconductor layer stack 2 is shown in plan view of the first top side 8a in Fig. 6C, as well as in the Fig. 6D and Fig. 6E shows sectional views along the lines AA and BB. In particular, the Fig. 6D and Fig. 6E show that the step-shaped design of the first front side 7a is limited to the area of ​​the first recess 15a.

[0070] The Fig. 7A to 7G show corresponding plan views of only the carrier substrate 2 during a step of the method for producing a laser device 1 according to the proposed principle, as well as detailed views and sectional views of the carrier substrate 11 of a resulting laser device 1.

[0071] In particular, the shape of the second recesses 15b and how they can be distributed within the carrier substrate 11 are shown. However, the illustrated shape in the form of pockets or the arrangement in the form of a matrix arrangement is to be understood as an example and can be varied. For example, differently shaped pockets in the form of circles, ovals, hexagons, octagons, etc. would also be conceivable. The pockets can be formed with a desired width b1 and a desired length 11 depending on requirements.

[0072] In Fig. 7A also shows that the electrical vias 12 can be arranged at different positions and, for example, extend either centrally through the carrier substrate 11 of a laser device 1, or in an edge region of a plurality of laser devices 1, so that per laser device only a partial region of the via 12 serves as a later via of the laser device 12. In the illustrated case, the pockets are rectangular and, in particular, designed such that they do not extend over the entire width of the second underside 9b of a later laser device, but only over a central region. Viewed from above, as also in the detailed view in Fig. 7B and Fig. 7E, an H-shaped second underside 9b can result. The length 11 of the pockets can, in particular, determine the depth by which the second section 13b is set back from a later-created first section 13a of the second front side 7b.

[0073] The figure also shows the dividing lines 20 along which the laser devices 1 are separated, resulting in the first sections 13a of the second front sides 7b and the seventh sections 13g of the second rear sides 16b. Due to the matrix arrangement of the pockets, dividing lines 20 are formed in two mutually perpendicular directions x, y, so that a plurality of laser devices 1 arranged in a matrix can be obtained.

[0074] Such a resulting laser device 1 or its carrier substrate 11 is shown in plan view of the second underside 9b in the Fig. 7B and Fig. 7E, as well as in the Fig. 7C and Fig. 7D or 7F and Fig. 7G are sectional views along the lines AA and BB. In particular, the Fig. 7C and Fig. 7D or 7F and Fig. 7G show that the stepped configuration of the second front side 7b is limited to the area of ​​the second recess 15b. In addition, the Fig. 7C and Fig. 7D or 7F and Fig. 7G shows possible arrangements and configurations of the electrical through-hole 12 in section. Fig. 7B and Fig. 7C can be designed as a TSV, for example, while the through-hole 12 shown in the Fig. 7E and Fig. 7G shown through-hole 12 can be formed by a coated through-hole.

[0075] The Fig. 8A to 8D and the Fig. 9A to 9E show an alternative to the Fig. 6A to 6E and the Fig.7A to 7G steps or views. In particular, the method and the resulting laser devices 1 differ in that the first and second recesses 15a, 15b are formed not by pockets, but by trenches, resulting in a stepped front side across the entire width of the laser device 1 for both the semiconductor layer stack 2 and the carrier substrate 11 of a laser device. LIST OF REFERENCE SYMBOLS 1 laser device 2 semiconductor layer stacks 3 active zones 4 first layer 5 second layer 6 Structure for current constriction 7a, 7b front 8a, 8b top 9a, 9b bottom 10 exit windows 11 Carrier substrate 12 vias 13a,..., 13h section 14 electrical contact layer 15a, 15b recess 16a, 16b back 17 Target substrate 18 wire contact 19 Separation mark 20 dividing line L Laser radiation b1, b2 width 11, 12 Length t1, t2 thickness x, y direction

Claims

[1] Optoelectronic laser device (1) comprising: a semiconductor layer stack (2) with an active zone (3) arranged between a first layer (4) of a first conductivity type and a second layer (5) of a second conductivity type, at least one structure (6) which is designed to constrict current in the active zone (3) to generate laser radiation (L), and a first front side (7a) which extends from a first upper side (8a) in the direction of a first lower side (9a) opposite the first upper side (8a) and has an exit window (10) for the laser radiation (L) generated in the active zone (3); a carrier substrate (11) with an electrical via (12) extending from a second top side (8b) to an opposite second bottom side (9b), and a second front side (7b) extending from the second underside (9b) in the direction of the second upper side (8b), the second front side (7b) having a first section (13a) adjoining the second upper side (8b) and a second section (13b) set back from the first section (13a); and an electrical contact layer (14) which is arranged on the first underside (9a) and is designed to be arranged on a contact element and which is in electrical connection with the first layer (4); wherein the first upper side (8a) and the second lower side (9b) are arranged touchingly next to each other; and wherein the electrical via (12) is in electrical connection with the second layer (5). [2] Optoelectronic laser device according to claim 1, wherein the first front side (7a) has a third section (13c) adjoining the first underside (9a) and a fourth section (13d) set back from the third section (13c). [3] Optoelectronic laser device according to claim 1 or 2, wherein the second section (13b) and the first front side (7a), in particular the fourth section (13d) of the first front side (7a), lie substantially in the same plane. [4] An optoelectronic laser device according to claim 2 or 3, wherein the first portion (13a) and the third portion (13c) lie substantially in the same plane. [5] Optoelectronic laser device according to one of the preceding claims, wherein the active zone (3) is arranged between two waveguide layers. [6] Optoelectronic laser device according to one of the preceding claims, wherein the fourth section (13d) is formed by a first recess (15a) in the semiconductor layer stack (2), which extends from the first upper side (8a) towards the first lower side (9a); and / or wherein the second portion (13b) is formed by a second recess (15b) in the carrier substrate (11), which extends from the second underside (9b) towards the second top side (8b). [7] Optoelectronic laser device according to the preceding claim, wherein the first recess (15a) extends over the entire width (b1) of the first upper side (8a) when viewed in plan view of the first upper side (8a); and / or wherein the second recess (15b) extends over the entire width (b2) of the second underside (9b) when viewed in plan view of the second underside (9b). [8] Optoelectronic laser device according to one of claims 6 to 7, wherein the first recess (15a) is formed by a pocket in the semiconductor layer stack (2) which, viewed in plan view of the first upper side (8a), does not extend over the entire width (b1) of the first upper side (8a), in particular over at most 200 µm of the width (b1) of the first upper side (8a); and / or wherein the second recess (15b) is formed by a pocket in the carrier substrate (11) which, when viewed in plan view of the second underside (9b), does not extend over the entire width (b2) of the second underside (9b), in particular over at most 200 µm of the width (b2) of the second underside (9b). [9] Optoelectronic laser device according to one of the preceding claims, wherein the semiconductor layer stack (2) has a thickness of at most 50 µm, in particular at most 30 µm, or at most 15 µm. [10] Optoelectronic laser device according to one of the preceding claims, wherein the active zone (3) is arranged at a distance closer to the first upper side (8a) than to the first lower side (9a). [11] Optoelectronic laser device according to one of the preceding claims, wherein the fourth section (13d) is set back from the third section (13c) by at most 100 µm, and in particular by at least 10 µm; and / or wherein the second section (13b) is set back from the first section (13a) by at most 100 µm, and in particular by at least 10 µm [12] Optoelectronic laser device according to one of the preceding claims, wherein the semiconductor layer stack (2) further comprises a first rear side (16a) opposite the first front side (7a) and extending from the first top side (8a) in the direction of the first bottom side (9a); and wherein optionally the first rear side (16a) has a fifth section (13e) adjoining the first underside (9a) and a sixth section (13f) set back from the fifth section (13e). [13] Optoelectronic laser device according to one of the preceding claims, wherein the carrier substrate (11) further comprises a second rear side (16b) opposite the second front side (7b) and extending from the second upper side (8b) in the direction of the second lower side (9b); and wherein the second rear side (16b) has a seventh section (13g) adjoining the second upper side (8b) and an eighth section (13h) set back from the seventh section (13g). [14] Method for producing a laser device (1), in particular a laser device according to one of the preceding claims, comprising the steps: Providing a semiconductor layer stack (2) with an active zone (3) arranged between a first layer (4) of a first conductivity type and a second layer (5) of a second conductivity type, and at least one structure (6) which is designed to constrict current in the active zone (3) for generating laser radiation (L); Creating at least one first recess (15a) in the semiconductor layer stack (2) such that a fourth section (13d) of a first front side (7a) of the semiconductor layer stack (2) is exposed, which section extends from a first top side (8a) of the semiconductor layer stack (2) through the second layer (5), the active zone (3) and into the first layer (4), and which exposes an exit window (10) for the laser radiation (L) generated in the active zone (3); Providing a carrier substrate (11) with an electrical via (12) extending from a second top side (8b) to an opposite second bottom side (9b), and at least one second recess (15b) extending from the second underside (9b) toward the second upper side (8b) and exposing a second portion (13b) of a second front side (7b); and Applying the first upper side (8a) to the second lower side (9b) in such a way that the first upper side (8a) and the second lower side (9b) are arranged touching one another, the electrical via (12) is in electrical connection with the second layer (5), and the first and second recesses (15a, 15b) are substantially opposite one another; Thinning the semiconductor layer stack (2) such that a first bottom side (9a) of the semiconductor layer stack (2) opposite the first top side (8a) is exposed; and Applying an electrical contact layer (14) on the first underside (9a), which is in electrical connection with the first layer (4) and which is designed to be arranged on a contact element. [15] Method according to claim 14, wherein the step of thinning the semiconductor layer stack (2) is carried out in such a way that the at least one first recess (15a) is opened from a side opposite the first upper side (8a); and / or that the semiconductor layer stack (2) has a thickness of at most 50 µm, in particular at most 30 µm, or at most 15 µm. [16] Method according to claim 14 or 15, further comprising severing at least the carrier substrate (11) in the region of the at least one second recess (15b), wherein the cutting exposes a first portion (13a) of the second front side (7b), which extends from the second upper side (8b) towards the second lower side (9b), and wherein the second section (13b) is set back from the first section (13a). [17] Method according to claim 16, wherein the step of severing comprises severing the semiconductor layer stack (2) in the region of the at least one first recess (15a), wherein by cutting through the semiconductor layer stack (2) a third section (13c) of the first front side (7a) is exposed, which extends from the first underside (9a) in the direction of the first top side (8a), and wherein the fourth section (13d) is set back from the third section (13c). [18] Method according to one of claims 14 to 17, wherein the step of applying the first upper side (8a) to the second lower side (9b) is carried out in such a way that the at least one first recess (15a) and the at least one second recess (15b) are substantially congruent with each other, in particular in such a way that the second section (13b) and the fourth section (13d) are substantially in the same plane. [19] Method according to one of claims 14 to 18, wherein the at least one first recess (15a) extends over the entire width (b1) of the first upper side (8a) when viewed in plan view of the first upper side (8a), and is in particular designed in the form of a trench; and / or wherein the at least one second recess (15b) extends over the entire width (b2) of the second underside (9b) when viewed in plan view onto the second underside (9b), and is designed in particular in the form of a trench. [20] Method according to one of claims 14 to 19, wherein the at least one first recess (15b) is formed by a pocket in the semiconductor layer stack (2) which, viewed in plan view of the first upper side (8a), does not extend over the entire width (b1) of the first upper side (8a), in particular over at most 200 µm of the width (b1) of the first upper side (8a); and / or wherein the at least one second recess (15b) is formed by a pocket in the carrier substrate (11) which, when viewed in plan view of the second underside (9b), does not extend over the entire width (b2) of the second underside (9b), in particular over at most 200 µm of the width (b2) of the second underside (9b). [21] Method according to one of claims 14 to 20, wherein the step of providing a semiconductor layer stack (2) comprises providing the semiconductor layer stack (2) with a plurality of structures (6) which are designed to constrict current in the active zone (3) for generating laser radiation (L); wherein the method comprises producing a plurality of first recesses (15a) in the semiconductor layer stack (2) such that a plurality of fourth sections (13d) of first front sides (7a) of the semiconductor layer stack (2) are exposed, each of which extends from a first top side (8a) of the semiconductor layer stack (2) through the second layer (5), the active zone (3) and into the first layer (4), and each of which exposes at least one exit window (10) for the laser radiation (L) generated in the active zone (3); and wherein the step of providing a carrier substrate (11) comprises providing the carrier substrate (11) with a plurality of second recesses (15b) extending from the second bottom side (9b) towards the second top side (8b) and exposing a plurality of second sections (13b) of second front sides (7b), and wherein the carrier substrate (11) has a plurality of electrical vias (12) extending from the second top side (8b) to the second bottom side (9b). [22] Method according to claim 21, wherein the step of severing separates a plurality of laser devices (1), each comprising at least one of the plurality of structures (6) and one of the plurality of exit windows (10), and each comprising at least one electrical via (12) that is in electrical connection to a portion of the second layer (5).

Images