Laser array with light emission through the substrate, and method for producing the laser array

Abstract

The invention relates to a laser array with light emission through a substrate (12) of the laser array, said laser array comprising: a plurality of lasers (14) on the substrate, said lasers each being designed as a vertical-cavity surface emitter (VCSEL), wherein the lasers (14) each have a semiconductor layered structure comprising a first Bragg mirror (18), a second Bragg mirror (20) and an active region (22) between the first and the second Bragg mirror (18, 20), wherein the plurality of lasers (14) are grouped to form one or more mutually spaced sub-arrays (24, 26, 28) of the laser array; at least one first metal layer (40) which is situated over the first Bragg mirror (18) and makes contact with the lasers (14) of the one or more sub-arrays (24, 26, 28) on a side, facing away from the substrate (12), of the active region (22) of the lasers (14); at least one second metal layer (44) which is situated over the first Bragg mirror (18), is galvanically separate from the at least one first metal layer (40) and makes contact with the lasers (14) of the one or more subarrays (24, 26, 28) on a side, facing toward the substrate (12), of the active layer (22) through at least one opening (42) in the semiconductor layered structure, wherein the at least one opening (42) extends as far as the substrate (12) or into the substrate (12) or as far as a layer between the substrate (12) and the active region (22); an insulating layer (48) which is situated over the at least one first and second metal layer (40, 44); a third metal layer (50) which is situated over the insulating layer (48), makes contact with the at least one first metal layer (40) through first openings (51) in the insulating layer (48) and extends over regions of the at least one first metal layer (40) and over regions of the at least one second metal layer (44); and a fourth metal layer (52) which is situated over the insulating layer (48), makes contact with the at least one second metal layer (44) through second openings (53) in the insulating layer (48), is galvanically separate from the third metal layer (50) and extends over regions of the at least one first metal layer (40) and of the at least one second metal layer (44). The invention also relates to a method for producing the laser array.

Description

[0001] Laser array with light emission through the substrate and method for producing the laser array

[0002] The invention relates to a laser array with light emission through a substrate of the laser array. The invention further relates to a method for producing such a laser array.

[0003] Vertical cavity surface-emitting semiconductor lasers, or VCSELs for short, are used as radiation sources in sensor technology or communications engineering, for example. VCSELs typically have a semiconductor layer structure in which semiconductor layers are grown epitaxially on a semiconductor substrate in a stacked arrangement. The semiconductor layer structure typically has a first Bragg mirror, an active region, and a second Bragg mirror, which together form an optical resonator. A Bragg mirror is also referred to as a DBR (Distributed Bragg Reflector). VCSELs can be designed as so-called top emitters, in which light emission occurs through a side of the semiconductor layer structure facing away from the substrate. In so-called bottom emitters, however, light emission occurs through the substrate.Through-substrate VCSELs offer several advantages over top-emitting devices, for example, because optics can be patterned directly into the substrate's surface. Bottom-emitting VCSELs are also suitable for surface-mounting technology, also known as SMT (surface-mounted technology) or SMD (surface-mounted device). The advantages of SMDs include miniaturization, smaller component dimensions, cost reduction, etc. The present invention specifically relates to an array of bottom-emitting VCSELs.

[0004] DE 102021 129 874 A1 discloses a bottom-emitting semiconductor laser component configured as an SMD. US 10 826 278 B2 discloses a laser array with light emission through the substrate, comprising a first metal layer, a second metal layer, and an insulating layer between the first and second metal layers, wherein the second metal layer is contacted with the first metal layer through partial openings in the insulating layer.

[0005] It is an object of the present invention to provide a laser array or VCSEL array with light emission through the substrate, which can be manufactured inexpensively and in a simple manner and which is particularly suitable for SMT.

[0006] A further object of the present invention is to provide a method for producing such a laser array.

[0007] The first-mentioned object is achieved by a laser array with light emission through a substrate of the laser array according to patent claim 1.

[0008] The laser array according to the invention with light emission through the substrate of the laser array has a plurality of lasers on the substrate. The lasers are each designed as VCSELs. The lasers each have a semiconductor layer structure comprising a first Bragg mirror, a second Bragg mirror, and an active region between the first and second Bragg mirrors. The first Bragg mirror is arranged on the side of the active region facing away from the substrate. The plurality of lasers are grouped into one or more spaced-apart subarrays of the laser array. The individual VCSELs can be defined, for example, by etching a plurality of mesae, with each mesa defining a laser. After the mesae have been formed by etching, oxidation can follow to define a current aperture.If the lasers are not defined as mesas, a current aperture can be defined by a proton implantation or a locally defined tunnel diode. The VCSELs are formed on the substrate in such a way that several lasers are grouped into a subarray. The lasers of a subarray do not have to be formed as individual lasers or mesas; rather, a subarray can be a connected region in which the lasers are interconnected. The term "laser" is therefore also generally understood in this description to refer to the light emission position.

[0009] The laser array according to the invention has one or more first metal layers that contact the lasers of the sub-array(s) on a side of the active region of the lasers facing away from the substrate. The at least one first metal layer contacts the lasers of a sub-array jointly. The individual lasers of a sub-array are thus addressed jointly. If multiple sub-arrays are present, each sub-array can be assigned a first metal layer, wherein the first metal layers are separated from one another. The first metal layer serves to contact the lasers of a sub-array according to a first polarity, for example, a p-polarity.

[0010] The laser array according to the invention has one or more second metal layers that are galvanically or electrically separated from the first metal layer(s) and that contact the lasers of one or more, for example, adjacent sub-arrays through at least one opening in the semiconductor layer structure on a side of the active layer facing the substrate, wherein the at least one opening can extend to the substrate or into the substrate or to a layer between the substrate and the active region. The at least one second metal layer contacts the lasers of the sub-array(s) together. The second metal layer contacts the lasers according to a polarity that is different from the polarity of the contacting of the lasers by the first metal layer. If the first metal layer contacts the lasers according to a p-polarity, the second metal layer contacts the lasers according to an n-polarity.If the first metal layer contacts the lasers according to an n-polarity, the second metal layer contacts the lasers according to a p-polarity. The at least one opening in the semiconductor layer structure can be easily realized by etching the semiconductor layer structure. Depending on the number of subarrays, several second metal layers can be distributed across the array.

[0011] The at least one first metal layer is arranged above the first Bragg mirror, i.e. the Bragg mirror which is located on the side of the active region facing away from the substrate. The second metal layer is arranged partly at a level below the active layer of the lasers and partly, i.e. on the top side, above the first Bragg mirror. Semiconductor layers can be arranged between the first Bragg mirror and the first and second metal layers. The at least one first and second metal layer can each be multilayered. The first and second metal layers can each have a first thin metal layer which directly contacts the lasers, and a second thick metal layer which is arranged on the first metal layer and is in contact with the first metal layer or is at least electrically connected to it. The metal(s) of the first metal layer can be different from the metal(s) of the second metal layer.

[0012] The laser array according to the invention further comprises an insulation layer above the at least one first and second metal layer. The insulation layer has openings in defined regions, i.e., the at least one first and second metal layer are exposed in these openings. A third metal layer is located above the insulation layer, which contacts the at least one first metal layer through first openings in the insulation layer and extends over regions of the first metal layer(s) and over regions of the second metal layer(s). In the regions of the second metal layer(s), the third metal layer is galvanically separated from the second metal layer(s) by the insulation layer.A fourth metal layer is located above the insulating layer, which contacts the second metal layer(s) through second perforations in the insulating layer, is galvanically isolated from the third metal layer, and extends over portions of the first metal layer(s) and the second metal layer(s). The fourth metal layer thus contacts the second or second metal layers, but does not contact the first or first metal layers, although it also extends over portions of the first metal layer(s).

[0013] In the following, if multiple subarrays and thus multiple first metal layers are present, these are collectively referred to as the first metal layer. If multiple second metal layers are present, these are collectively referred to as the second metal layer.

[0014] The advantage of the laser array according to the invention is that the third metal layer and the fourth metal layer can be formed over a large area yet sufficiently spaced from one another, making the third and fourth metal layers particularly well-suited as solder pads for soldering electronic components. The first metal layer and the second metal layer can have comparatively thick metal layers, in particular strip-shaped metal layers, on their sides facing the third and fourth metal layers, as described above. The third and fourth metal layers can also be formed as thick metal layers. Overall, the laser array according to the invention can be manufactured simply and cost-effectively.

[0015] The third metal layer serves to contact the lasers via the first metal layer according to a first polarity, for example, p-polarity, and the fourth metal layer serves to contact the lasers via the second metal layer according to a second polarity, for example, n-polarity. The third and fourth metal layers can thus form the anode and cathode of the laser array.

[0016] The first metal layer extends over the lasers of a respective sub-array. The second metal layer, however, is preferably arranged in a region or regions outside the sub-array(s). If the laser array has at least two sub-arrays that are spaced apart from each other, the second metal layer is preferably arranged in an intermediate region between the sub-arrays.

[0017] In this configuration, the lasers are contacted on the side of the active region facing the substrate, thus in the non-light-emitting areas of the array. In the case of strip-shaped rectangular subarrays, this has the advantage that the lasers of a subarray have identical current paths to the individual lasers.

[0018] In addition or alternatively to the aforementioned configuration, the second metal layer can surround the sub-array(s) along an outer periphery of the sub-array(s). This has the advantage that the sub-arrays can be arranged closer together, since the area between the sub-arrays is not required, or only required to a lesser extent, for contacting the lasers via the second metal layer.

[0019] Preferably, the at least one opening in the semiconductor layer structure has an elongated shape in the direction parallel to the plane of the substrate with an aspect ratio of greater than 10, optionally greater than 20, further optionally greater than 40.

[0020] The advantage here is that the openings, due to their elongated shape, maximize the open area of ​​the layer exposed during etching of the opening, for example the n-doped layer, while the size of the opening transverse to its longitudinal extent is small for, for example, the application of the second metal layer (substrate-side contact) to the exposed semiconductor layer, so that the distance between the substrate-side contact and the lasers is advantageously short.

[0021] The at least one opening in the semiconductor layer structure can have an elongated shape in the direction parallel to the plane of the substrate, with a short side length of less than 20 pm, optionally less than 15 pm, further optionally less than 10 pm. Since the at least one opening in the semiconductor layer structure extends deep into the semiconductor layer structure, a very small dimension of the at least one opening transverse to its longitudinal extent is advantageous with respect to the deposition of the second metal layer, which contacts the lasers on the substrate-side side of the active layer.

[0022] Preferably, the sub-array(s) has / have the shape of a rectangle, with at least one side of the rectangle running parallel to the at least one opening in the semiconductor layer structure and preferably having substantially the same length as the at least one opening. It is advantageous that the distance of each laser of the sub-array(s) from its nearest substrate-side contact is substantially the same for all lasers. This results in current paths of substantially equal length from the substrate-side contact to the individual lasers.

[0023] In connection in particular with the above-mentioned embodiment, according to which the second metal layer surrounds the sub-array or the sub-arrays on an outer circumference of the sub-array or sub-arrays, it is further preferred if the at least one opening in the semiconductor layer structure surrounds the sub-array or sub-arrays on an outer circumference of the sub-array or sub-arrays.

[0024] Further preferably, the third and fourth metal layers have the same height above the substrate. This is particularly advantageous for the laser array's suitability as an SMD.

[0025] Furthermore, it is preferred if the third and fourth metal layers have the same shape and / or surface dimensions. This measure is also advantageous with regard to the suitability of the laser array as an SMD.

[0026] It is also preferred if the first and second metal layers have the same height above the substrate on the top side. This measure is particularly advantageous with regard to the manufacturing process of the laser array, in order to simplify the application of the insulation layer, the perforations in the insulation layer, and the application of the third and fourth metal layers.

[0027] Preferably, with regard to the suitability of the laser array according to the invention as an SMD, the third and fourth metal layers have a distance of more than 100 pm, optionally more than 150 pm and less than 300 pm from each other.

[0028] Furthermore, the invention provides a method for producing a laser array with light emission through a substrate of the laser array according to claim 13. The advantages of the inventive manufacturing method arise from the advantages of the inventive laser array. Likewise, preferred embodiments of the inventive manufacturing method arise from the preferred embodiments of the inventive laser array.

[0029] In the manufacturing method, the at least one opening in the semiconductor layer structure is produced by etching the semiconductor layer structure down to the substrate or into the substrate or down to a layer between the substrate and the active region.

[0030] Further advantages and features can be found in the following description and the attached drawing.

[0031] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified but also in other combinations or on their own without departing from the scope of the invention.

[0032] Embodiments of the invention are illustrated in the drawings and are described in more detail below with reference to them. They show:

[0033] Fig. 1 shows a plan view of a laser array in a first stage of its manufacture; Fig. 1A shows a section through a resonator region of an individual laser of the array;

[0034] Fig. 2 shows the laser array in Fig. 1 in plan view at a further stage of its manufacture;

[0035] Fig. 3 shows the laser array in Fig. 2 in plan view at a further stage of its manufacture;

[0036] Fig. 3A is a cross-sectional view of part of the laser array in Fig. 3;

[0037] Fig. 4 shows the laser array in Fig. 3 in plan view at a further stage of its manufacture;

[0038] Fig. 4A is a cross-sectional view of part of the laser array in Fig. 4;

[0039] Fig. 5 shows the laser array in Fig. 4 in plan view at a further stage of its manufacture;

[0040] Fig. 5A is a cross-sectional view of part of the laser array in Fig. 5;

[0041] Fig. 6 shows the laser array in Fig. 5 in plan view at a further stage of its manufacture;

[0042] Fig. 7 shows the laser array in Fig. 6 in plan view in a final stage of its manufacture;

[0043] Fig. 8 shows a modified embodiment of a laser array in plan view at one stage of its manufacture; Fig. 9 shows the laser array in Fig. 8 in plan view at a further stage of its manufacture;

[0044] Fig. 10 shows the laser array in Fig. 9 in plan view at a further stage of its manufacture; and

[0045] Fig. 11 shows a plan view of the laser array in Fig. 10 in a final stage of its manufacture.

[0046] With reference to Figs. 1 to 7, a first embodiment of a laser array 10 with light emission through a substrate 12 (Fig. 1A) of the laser array 10 is described. Figs. 1 to 7 show the structure and the individual stages of manufacturing the laser array 10.

[0047] The laser array 10 has a plurality of lasers 14, the positions of which are defined, for example, by etching a plurality of mesas. The mesas created by the etching are separated from one another by trenches 16. The individual lasers each have a semiconductor layer structure, which is shown schematically in Fig. 1A and has a first Bragg mirror 18, a second Bragg mirror 20, and an active region 22 between the first and second Bragg mirrors on the substrate 12. The first Bragg mirror 18 can be p-doped, and the second Bragg mirror 20 can be n-doped, or vice versa. The light emission through the substrate 12 is indicated by an arrow 13. The plurality of lasers 14 are grouped into one or more spaced-apart subarrays 24, 26, and 28. In the example shown, the laser array 10 has three subarrays. However, more or fewer than three sub-arrays are possible.

[0048] As shown, the sub-arrays 24, 26, and 28 preferably have an elongated rectangular shape. A respective region 30 and 32 between the sub-arrays 24 and 26, or 26 and 28, also has an elongated rectangular shape. The regions 30 and 32 not occupied by lasers 14 serve as regions for contacting the lasers 14 on the side of the active region 22 facing the substrate, as will be described later. This allows the current path from these contacts to the lasers 14 to be kept short and the same or at least similar for all lasers 14.

[0049] If the lasers 14 are produced from the semiconductor layer structure, which can be produced epitaxially, by etching mesenas, the etching can be followed by oxidation to create a current aperture. However, a current aperture can also be defined by proton implantation or locally by tunnel junctions, etc. Fig. 1 shows three possible different configurations of the lasers 14. In the sub-array 24, the lasers 14 are each formed as individual lasers 14. The sub-array 26, on the other hand, is a connected region in which the lasers are connected to one another at diagonal connection points 34. Such a configuration has the advantage of a possible smaller distance between the lasers and increased mechanical stability of the array. In the sub-array 28, the connection points 34 even extend into the non-lasing outer peripheral region 36 of the array 10, and the mechanical stability is thereby further improved.

[0050] It is understood that the sub-arrays 24, 26 and 28 of the laser array can be identical to one another, ie the laser array 10 can have in all sub-arrays 24, 26, 28 either the design according to the sub-array 24, according to the sub-array 26 or the sub-array 28.

[0051] Furthermore, Fig. 1 shows, by way of example, a region 38 which can also serve to contact the lasers on the side of the active region 22 facing the substrate 12 and is insulated from the lasering regions, for example by etching or proton implantation.

[0052] Starting from Fig. 1, Fig. 2 shows a further stage of the laser array 10 during its manufacture. In this stage, contacts 40A are realized on the lasers 14, i.e. on the side of the active region 22 facing away from the substrate 12. The contacts 40A can be p-contacts, for example. This is not mandatory, however; the contacts 40A can also be n-contacts. In the exemplary embodiment described further below, the contacts 40A are designed as p-contacts. The contacts 40A are a metal layer of a respective first metal layer 40 above the first Bragg mirror 18. Preferably, a passivation layer is applied around the mesas (laser 14) before or after the metallization to produce the contacts 40A. Since the array 10 in the example shown has three sub-arrays 24, 26, 28, three first metal layers 40 are present, one on each sub-array 24, 26, 28.However, these are referred to collectively as the first metal layer 40 below.

[0053] Starting with Fig. 2, Fig. 3 and Fig. 3A show the laser array 10 in a further stage of its fabrication. In this stage, deep openings or holes 42 in the form of slots are etched into the semiconductor layer structure in the isolated regions 30 and 32, i.e., between the sub-arrays 24, 26, and 28. The openings 42 have an elongated shape and run parallel to the long sides of the sub-arrays 24, 26, 28. The length of the openings is equal to or substantially equal to the length of the long sides of the sub-arrays 24, 26, 28.

[0054] The elongated openings 42 are shown in cross-section in Fig. 3A. The openings 42 can extend into the substrate 12 or a contact layer between the substrate 12 and the second Bragg mirror 20, or only into the second Bragg mirror 20. In the exemplary embodiment, the openings or holes 42 have an elongated shape, thereby maximizing the open area of ​​the exposed (n-doped) contact layer, while the size of each opening or hole 42 in a direction transverse to its longitudinal extent advantageously remains small for the subsequent two steps.

[0055] Preferably, the openings 42 in the semiconductor layer structure have an elongated shape in the direction parallel to the plane of the substrate 12 with an aspect ratio of greater than 10, optionally greater than 20, further optionally greater than 40. The openings or holes 42 can have a short side length of less than 20 pm, optionally less than 15 pm, further optionally less than 10 pm. As shown in Fig. 3, the openings or holes 42 run parallel to the long sides of the sub-arrays 24, 26 and 28 and, as described above, preferably have the same length as the sub-arrays 24, 26 and 28. This also creates essentially identical or at least very similar current paths from the substrate-side contact to the lasers 14 on the side of the active region 22 facing the substrate 12.

[0056] Starting from Fig. 3, Fig. 4 shows the laser array 10 in a further stage of its manufacture. The illustration in Fig. 4 is rotated by 90° compared to the illustration in Fig. 3. In this stage, a second metal layer 44 is applied above the first Bragg mirror 18 in the regions 30 and 32 in which the openings 42 are present, which is galvanically or electrically separated from the first metal layer 40, i.e. the contacts 40A. The second metal layer 44 forms contacts 44A which contact the lasers 14 through the openings 42 in the semiconductor layer structure on a side of the active layer 22 facing the substrate 12. The second metal layer 44 is deposited on the bottoms of the openings 42, as shown in Fig. 4A.Since lithographic structuring in the deep and narrow openings 42 is not possible or not easy, a defined region 46 is preferably also covered with the metal of the second metal layer 44, as shown in Fig. 4A. Furthermore, the sidewalls of the deep openings 42 are also preferably metallized (not shown) to enable easier filling of the openings 42 in the subsequent step. Corresponding to the number of three sub-arrays 24, 26, 28, two separate second metal layers 44 are present in the illustrated embodiment. However, these are collectively referred to as the second metal layer 44 in the present description.

[0057] Starting from Fig. 4, Figs. 5 and 5A show the laser array 10 in a further stage of its manufacture. Fig. 5 has the same orientation as Fig. 4. At this stage, thick first metal layers 40B are applied to the sub-arrays 24, 26 and 28, which contain the lasers 14. More precisely, the metal layers 40B are applied to the contacts 40A and thus complete the first metal layer 40. The first metal layer 40 thus extends over all lasers 14 of the respective sub-arrays 24, 26 and 28 and serves to contact the lasers 14 on the side of the active region 22 facing away from the substrate 12. Likewise, at this stage, a second thick metal layer 44B is applied to the intermediate regions 30 and 32, completing the second metal layer 44. Preferably, the thick first and second metal layers 40B and 44B are applied by electrodeless electroplating, which allows thick metal layers.The thickness of the second metal layer 44B should be large enough to at least partially, preferably completely, fill the deep openings 42 with the metal, as shown in Fig. 5A, such that an electrical connection from the n-contact of the n-doped region is realized to the same extent as the p-contact, as shown in Fig. 5A. The first and second metal layers 40, 44 preferably have the same height level above the substrate 12 on the top side. Fig. 5A further shows a passivation layer 47 on the Bragg mirror 18 and a barrier layer 49 on the thick metal layer 44B.

[0058] Starting with Fig. 5, Fig. 6 shows the laser array 10 in a further stage of its manufacture. Fig. 6 is rotated 90° compared to the illustration in Fig. 5, thus having the same orientation as Fig. 3. In this stage, an insulating layer or passivation layer 48 is applied to the first and second metal layers 40, 44, more precisely to the metal layers 40B and 44B, which passivates the surface of the metal layers 40 and 44. Openings or vias 51, 53 are introduced into the insulating layer 48, through which the metal layers 40 (40B) and 44 (44B) are partially exposed.

[0059] Starting from Fig. 6, Fig. 7 shows a final stage of the laser array 10. Fig. 7 has the same orientation as Fig. 6. In this stage, a third metal layer 50 and a fourth metal layer 52 have been applied over the insulation layer 48. The metal layers 50 and 52 are also formed as thick metal layers. The third metal layer 50 contacts the first metal layer 40 via the openings 51 in the insulation layer 48. The third metal layer 50 extends over regions of the first metal layer 40 and over regions of the second metal layer 44, as can be seen from Figs. 6 and 7, but is insulated from the second metal layer 44 by the insulation layer 48. The fourth metal layer 52 above the insulation layer 48 contacts the second metal layer 44 through second openings 53 in the insulation layer 48. The fourth metal layer 52 is galvanically separated from the third metal layer 50 by the insulation layer 48.The fourth metal layer 42 also extends over portions of the first metal layer 40 and the second metal layer 44, as shown in Figs. 6 and 7, but is insulated from the first metal layer 40 by the insulation layer 48.

[0060] In the present embodiment, the third metal layer 50 serves as the anode and the fourth metal layer 52 as the cathode of the laser array 10.

[0061] The third metal layer 50 thus contacts the lasers on the side of the active layer 22 facing away from the substrate 12, and the fourth metal layer 52 contacts the lasers 14 on the side of the active layer 22 facing the substrate 12.

[0062] The thick metal layers 40 and 44 due to the thick metal layers 40B and 44B on the one hand and the thick metal layers 50 and 52 on the other hand as well as the insulation layer 48 between the metal layers 40, 44 on the one hand and the metal layers 50, 52 on the other hand enable a decoupling of the solder connection side of the array 10 from the contact side of the anode and cathode contact of the lasers 14. The laser array 10 is easily suitable for reflow soldering with solder paste, as is used in SMT, since the soldering pads, i.e. the top sides of the metal layers 50 and 52, can be large and a sufficiently large distance, typically > 100 pm, preferably > 150 pm, between the soldering pads on the metal layers 50 and 52 is possible, while at the same time the arrangement of the lasers 14 and the substrate-side contacts can be optimized independently of one another.For the latter, a fine structure is provided in the laser array 10, which minimizes the distance from the substrate-side contact to the lasers, while at the same time utilizing as much of the chip area as possible for lasers. At the same time, the lasers can be distributed across most of the chip area, resulting in better thermal management compared to a chip design in which the same number of lasers is clustered in one part of the chip.

[0063] In particular, the third and fourth metal layers 50 and 52 can have the same height above the substrate 12 on the top side, which is beneficial for the further processing of the laser array 10 as an SMD. In the illustrated embodiment, the third and fourth metal layers 50 and 52 have the same shape and / or surface dimensions, which is also advantageous.

[0064] In particular, the first and second thick metal layers 40A, 40B and 44A, 44B for contacting the lasers on the anode and cathode sides result in fewer processing steps in the manufacture of the laser array. Since these thick metal layers further planarize the chip, a thin insulation layer 48 and the third and fourth metal layers 50 and 52 can be created with simple processing steps and used to realize large solder contacts at the same height level. Both solder contact areas on the metal layers 50 and 52 can extend over both the first and second thick metal layers 40A, 40B and 44A, 44B.

[0065] With reference to Figs. 8 to 11, a modified embodiment of a laser array 10' with light emission through the substrate 12 of the laser array 10' is described. Only the differences between the laser array 10' and the laser array 10 are described. Elements of the laser array 10' that are identical, similar, or comparable to elements of the laser array 10 are provided with the same reference numerals, supplemented by a prime.

[0066] Fig. 8 shows the laser array 10' in a stage corresponding to the stage of the laser array 10 in Fig. 3. The difference to the laser array 10 is that the sub-arrays 24', 26' and 28' with the lasers 14' are again formed as rectangles, but the intermediate regions 30' and 32' between the sub-arrays 24', 26' and 28' are narrower than the intermediate regions 30 and 32 of the laser array 10. The outer region 36' and regions 37' between the sub-arrays 24', 26' and 28' are insulated by ion implantation. In the intermediate regions 30' and 32' there is only one deep opening 42' in the semiconductor layer structure, while a further opening 80' in the semiconductor layer structure for contacting the lasers on the side of the active layer 22 facing the substrate 12 surrounds the sub-arrays 24', 26', 28' on their outer circumference.The sub-arrays 24', 26', and 28' can thus be arranged at a closer distance from one another, since the outer area around the sub-arrays is also used for the substrate-side contacting of the lasers 14'. Fig. 9 shows a stage of the laser array 10' that corresponds to the stage of the laser array 10 in Fig. 5. The first metal layer 40' here again covers the lasers 14' for contacting the lasers 14' on the side of the active region 22' facing away from the substrate 12'. The second metal layer 44' is located between the sub-arrays 24', 26', and 28' and, in addition, corresponding to the opening 80', it surrounds the sub-arrays 24', 26', and 28' at their outer circumference and serves for the substrate-side contacting of the lasers 14'.

[0067] Fig. 10 shows the laser array 10' at a stage of its manufacture that corresponds to the stage of the laser array 10 in Fig. 6. Here, openings 5T and 53' are again present in the insulation or passivation layer 48', which partially expose the first and second metal layers 40', 44'.

[0068] Fig. 11 shows the laser array 10' in a stage corresponding to the stage of the laser array 10 in Fig. 7. In Fig. 11, the third metal layer 50' and the fourth metal layer 52' ​​are applied to the insulation layer 48', with the third metal layer 50' forming the cathode and the fourth metal layer 52' ​​forming the anode of the laser array 10' for contacting the lasers 14'.

[0069] In this embodiment, the annular second metal layer 44' also forms a protective ring to protect the lasers 14' from moisture when the lasers 14' are not realized by a complete trench or mesa etching, but rather when only perforations in the semiconductor layer structure are etched on four or more sides. Thus, although several lasers 14' are formed after oxidation, the lasers 14' are connected to their neighbors via the complete semiconductor layer structure. In addition, ion implantation is used here to electrically separate the lasers 14' from the regions in which the substrate-side contact is formed in and around the deep perforations in the semiconductor layer structure.

Claims

Patent claims 1. A laser array with light emission through a substrate (12) of the laser array, the laser array comprising: a plurality of lasers (14) on the substrate, each configured as a vertical cavity surface emitter (VCSEL), the lasers (14) each having a semiconductor layer structure comprising a first Bragg mirror (18), a second Bragg mirror (20), and an active region (22) between the first and second Bragg mirrors (18, 20), the plurality of lasers (14) being grouped into one or more spaced-apart sub-arrays (24, 26, 28) of the laser array; at least one first metal layer (40) contacting the lasers (14) of the sub-array(s) (24, 26, 28) on a side of the active region (22) of the lasers (14) facing away from the substrate (12);at least one second metal layer (44) which is galvanically separated from the at least one first metal layer (40) and which contacts the lasers (14) of the sub-array(s) (24, 26, 28) through at least one opening (42) in the semiconductor layer structure on a side of the active layer (22) facing the substrate (12), wherein the at least one opening (42) extends as far as the substrate (12) or into the substrate (12) or as far as a layer between the substrate (12) and the active region (22); an insulation layer (48) over the at least one first and second metal layer (40, 44); a third metal layer (50) over the insulation layer (48), which contacts the at least one first metal layer (40) through first openings (51) in the insulation layer (48) and extends over regions of the at least one first metal layer (40) and over regions of the at least one second metal layer (44);and a fourth metal layer (52) over the insulation layer (48), which contacts the at least one second metal layer (44) through second openings (53) in the insulation layer (48), galvanically from the third metal layer (50); is separated and extends over regions of the at least one first metal layer (40) and the at least one second metal layer (44).

2. Laser array according to claim 1, wherein the at least one second metal layer (44) is arranged in a region or regions outside the sub-array or sub-arrays (24, 26, 28).

3. Laser array according to claim 1 or 2, wherein the laser array has at least two sub-arrays (24, 26, 28), and wherein the at least one second metal layer (44) is arranged in an intermediate region between adjacent sub-arrays (24, 26, 28).

4. Laser array according to one of claims 1 to 3, wherein the at least one second metal layer (44) surrounds the sub-array(s) (24, 26, 28) at an outer periphery of the sub-array(s) (24, 26, 28).

5. Laser array according to one of claims 1 to 4, wherein the at least one first and the at least one second metal layer (40, 44) each comprise a thick metal layer (40B, 44B).

6. Laser array according to one of claims 1 to 5, wherein the at least one opening (42) in the semiconductor layer structure in the direction parallel to the plane of the substrate (12) has an elongated shape with an aspect ratio of greater than 10, optionally greater than 20, further optionally greater than 40.

7. Laser array according to one of claims 1 to 6, wherein the at least one opening (42) in the semiconductor layer structure in the direction parallel to the plane of the substrate (12) has an elongated shape with a length of the short side of less than 20 pm, optionally less than 15 pm, further optionally less than 10 pm.

8. Laser array according to claim 6 or 7, wherein the sub-array(s) (24, 26, 28) have the shape of a rectangle, wherein at least one side of the rectangle runs parallel to the at least one opening (42) in the semiconductor layer structure and preferably has substantially the same length as the at least one opening (42).

9. Laser array according to one of claims 1 to 8, wherein the at least one opening (42) in the semiconductor layer structure surrounds the sub-array(s) on an outer periphery of the sub-array(s) (24, 26, 28).

10. Laser array according to one of claims 1 to 9, wherein the third and fourth metal layers (50, 52) have the same height level above the substrate (12) on the upper side.

11. Laser array according to one of claims 1 to 10, wherein the third and fourth metal layers (50, 52) have the same shape and / or surface dimension.

12. Laser array according to one of claims 1 to 11, wherein the first and second metal layers (40, 44) have the same height level above the substrate (12) on the upper side.

13. Laser array according to one of claims 1 to 12, wherein the third and fourth metal layers (50, 52) have a lateral distance of more than 100 pm, optionally more than 150 pm, and less than 300 pm from each other.

14. A method for producing a laser array with light emission through a substrate (12) of the laser array, comprising the steps: Producing a plurality of lasers (14) on the substrate (12), each of which is configured as a vertical cavity surface emitter (VCSEL), wherein the plurality of lasers (14) are grouped into one or more spaced-apart sub-arrays (24, 26, 28) of the laser array; wherein the lasers (14) each have a semiconductor layer structure comprising a first Bragg mirror (18), a second Bragg mirror (20), and an active region (22) between the first and second Bragg mirrors (18, 20); Applying at least one first metal layer (40) over the first Bragg mirror (18), which contacts the lasers (14) of the sub-array(s) (24, 26, 28) on a side of the active region (18) of the lasers (14) facing away from the substrate (12); Applying at least one second metal layer (44) over the first Bragg mirror (18), which is galvanically isolated from the at least one first metal layer (40) and which contacts the lasers (14) of the sub-array(s) (24, 26, 28) through at least one opening (42) in the semiconductor layer structure on a side of the active layer (22) facing the substrate (12), wherein the at least one opening (42) extends as far as the substrate (12) or into the substrate (12) or as far as a layer between the substrate (12) and the active region (22); Applying an insulating layer (48) over the at least one first and second metal layer (40, 44); Applying a third metal layer (50) over the insulation layer (48), which third metal layer contacts the first metal layer (40) through first openings (51) in the insulation layer (48) and extends over regions of the at least one first metal layer (40) and over regions of the at least one second metal layer (44); and Applying a fourth metal layer (52) over the insulation layer (48), which fourth metal layer contacts the at least one second metal layer (44) through second openings (53) in the insulation layer (48), is galvanically separated from the third metal layer (50) and extends over regions of the at least one first metal layer (40) and the at least one second metal layer (44).

15. The method according to claim 14, wherein the at least one opening (42) in the semiconductor layer structure is produced by etching the semiconductor layer structure down to the substrate (12) or into the substrate (12) or down to a layer between the substrate (12) and the active region (22).

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