Optoelectronic component and method for its manufacture

Abstract

Method for manufacturing an optoelectronic device (10) comprising the following steps: - Providing a semiconductor crystal (100) having a surface (110); - Applying a first layer (200) having a dielectric to the surface (110); - Applying and structuring a photoresist layer (300) on the first layer (200), wherein the photoresist layer (300) is structured such that it has an opening (310); - Partial removal of the first layer to expose a first and a second lateral area (120, 121, 122) of the surface (110), wherein in a third lateral area (11) the first layer (200) is arranged on the surface, wherein the photoresist layer (300) is partially undercut during the removal of the first layer (200); - Applying a contact surface (410) having a first metal in the first lateral area (121) of the surface (110); - Removal of the photoresist layer (300); - Applying a second layer (500) comprising an optically transparent, electrically conductive material to the contact surface (410) and the second lateral area (120, 122) of the surface (110); - Applying a third layer (600) which has a second metal, onto the second layer (500).

Description

[0001] The present invention relates to a method for producing an optoelectronic component according to claim 1 and to an optoelectronic component according to claim 9.

[0002] For optoelectronic components with semiconductor crystals, it is necessary to reproducibly design contact surfaces for electrical contact with an optimal contact size. For example, for light-emitting diode components, it is necessary to reproducibly manufacture optimally dimensioned contact surfaces to achieve low forward voltages and high luminous efficacy.

[0003] For the production of light-emitting diode (LED) chips using thin-film technology, a process is known in the art in which a metal contact surface is created in a first lithographic process step. In a second process step, a layer of a mirror dielectric is applied, covering the contact surface. Using a photolithographic process, the mirror dielectric is then opened in the area of ​​the contact surface. A mirror metal is then deposited, which also serves to electrically contact the contact surface. Due to alignment tolerances during the lithographic process step, this process results in variation in the effective size of the contact surface.

[0004] The document DE 10 2010 049 186 A1 describes an optoelectronic component and a method for its production.

[0005] The documents EP 2 390 934 A2 and DE 20 2010 017 388 U1 describe light-emitting devices.

[0006] The document DE 102 61 364 B4 describes processes for producing a temperable multi-layer contact coating.

[0007] The document US 2004 / 0 114 652 A1 describes a method for producing a conductive structure, for example an electrode, and a surface-emitting semiconductor laser.

[0008] One object of the present invention is to provide a method for producing an optoelectronic component. This object is achieved by a method having the features of claim 1. A further object of the present invention is to provide an optoelectronic component. This object is achieved by an optoelectronic component having the features of claim 5. Various further developments are specified in the dependent claims.

[0009] A method for producing an optoelectronic component comprises steps of providing a semiconductor crystal having a surface, applying a first layer comprising a dielectric to the surface, applying and patterning a photoresist layer on the first layer, wherein the photoresist layer is patterned to have an opening, partially dissolving the first layer to expose a lateral region of the surface, applying a contact area comprising a first metal in the lateral region of the surface, removing the photoresist layer, applying a second layer comprising an optically transparent, electrically conductive material, and applying a third layer comprising a second metal.This method advantageously produces an optoelectronic component comprising a semiconductor crystal with a contact area whose size can be determined by the size of the opening in the photoresist layer. This advantageously makes it possible to determine the size of the contact area with high precision and reproducibility. The contact area advantageously serves, over its entire size, to electrically contact the semiconductor crystal, eliminating the need to make the contact area larger than necessary to compensate for a tolerance. This advantageously minimizes absorption of light generated in the semiconductor crystal at the contact area, allowing the optoelectronic component produced by the method to exhibit a higher light yield.A further advantage of the process is that it requires only one photolithographic process step, making the process cost-effective.

[0010] In one embodiment of the method, the photoresist layer comprises a positive resist. Advantageously, to pattern the photoresist layer, only the area in which the opening is to be created needs to be exposed.

[0011] In one embodiment of the method, the partial removal of the first layer is carried out by wet chemical etching.

[0012] Advantageously, the process is simple and cost-effective to carry out.

[0013] In one embodiment of the method, the photoresist layer is partially underetched during the removal of the first layer. This partial underetching advantageously ensures that the size of the generated contact area corresponds with high accuracy to the size of the opening in the patterned photoresist layer.

[0014] An optoelectronic component comprises a semiconductor crystal with a surface having a first lateral region, a second lateral region, and a third lateral region. In the first lateral region, a contact area comprising a first metal is arranged on the surface. In the third lateral region, a first layer comprising a dielectric is arranged on the surface. A second layer comprising an optically transparent, electrically conductive material is arranged on the contact area, the first layer, and the second lateral region of the surface. A third layer comprising a second metal is arranged on the second layer. Advantageously, in this optoelectronic component, the entire area of ​​the contact area serves to electrically contact the semiconductor crystal, whereby the contact area can be designed with small dimensions.This advantageously reduces light absorption at the contact surface, which can improve the luminous efficacy of the optoelectronic component. One advantage is that light absorption in the second lateral region is significantly lower than light absorption in the first lateral region at the contact surface. As a result, both the forward voltage of the optoelectronic component and the luminous efficacy of the optoelectronic component are virtually independent of the size of the second lateral region. This enables simple and cost-effective production of the optoelectronic component. A further advantage can be that the second layer serves as an adhesion promoter between the first and third layers.

[0015] In one embodiment of the optoelectronic component, a specific contact resistance between the second layer and the semiconductor crystal is at least one order of magnitude greater than a specific contact resistance between the contact area and the semiconductor crystal. Advantageously, the second layer is thus electrically connected to the semiconductor crystal to a much lesser extent than the contact area. This results in a forward voltage of the optoelectronic component being determined solely by the contact area. This advantageously results in a high reproducibility of the forward voltage.

[0016] In one embodiment of the optoelectronic component, the second lateral region surrounds the first lateral region in a ring-like manner, at least in part. Advantageously, the second lateral region thereby forms a safety distance between the contact area and the first layer of the optoelectronic component. This enables the contact area to be manufactured with a reproducible size.

[0017] In one embodiment of the optoelectronic component, the third lateral region surrounds the second lateral region in an annular manner, at least in part. Advantageously, the contact area is thus arranged in an opening of the first layer and spaced from the first layer, allowing the contact area to be produced with a readily reproducible size.

[0018] In one embodiment of the optoelectronic component, the optically transparent, electrically conductive material is a transparent, electrically conductive oxide. Transparent, electrically conductive oxides advantageously exhibit low optical absorption and electrically connect to semiconductor crystals with high contact resistance. Transparent, electrically conductive oxides are nevertheless advantageously suitable for electrically contacting the contact surface.

[0019] In one embodiment of the optoelectronic component, the first metal and / or the second metal is gold or silver. These metals advantageously have favorable optical and electrical properties.

[0020] In one embodiment of the optoelectronic component, the dielectric comprises SiO2. This advantageously improves the reflectivity of the third layer.

[0021] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings. In each case, in a schematic representation, Fig. 1 a semiconductor crystal for producing an optoelectronic component; Fig. 2 the semiconductor crystal with an applied first layer; Fig. 3 the first layer with a structured photoresist layer arranged thereon; Fig. 4 the first layer after partial removal of the first layer; Fig. 5 the semiconductor crystal, the first layer and the photoresist layer after the application of a metal layer; Fig. 6 the semiconductor crystal, the first layer and a contact surface after removal of the photoresist layer; Fig. 7 the unfinished optoelectronic component after the application of a second layer; Fig. 8 the unfinished optoelectronic component after the application of a third layer; and Fig. 9 the optoelectronic component after the application of a fourth layer.

[0022] Fig. Figure 1 shows a highly schematic cross-sectional view of a semiconductor crystal 100. The semiconductor crystal 100 can be produced, for example, by epitaxial growth. The semiconductor crystal 100 has a surface 110.

[0023] The semiconductor crystal 100 is intended for the production of an optoelectronic component, which requires further processing steps, which are explained below. The optoelectronic component can be, for example, a light-emitting diode component.

[0024] Fig. 2 shows the semiconductor crystal 100 in a schematic sectional view in one of the representations of the Fig. 1 chronologically subsequent processing stage. A planar first layer 200 has been arranged on the surface 110 of the semiconductor crystal 100. The first layer 200 has a dielectric that serves as a mirror dielectric. The first layer 200 can, for example, comprise silicon dioxide (SiO 2 ). The first layer 200 can, for example, have been applied to the surface 110 of the semiconductor crystal 100 by chemical vapor deposition.

[0025] Fig. 3 shows a schematic sectional view of the semiconductor crystal 100 in one of the representations of the Fig. 2 chronologically subsequent processing stage. A photoresist layer 300 has been arranged on the side of the first layer 200 facing away from the semiconductor crystal 100. The photoresist layer 300 has also been structured to create an opening 310 in the photoresist layer 300, through which the first layer 200 is accessible. The opening 310 in the photoresist layer 300 preferably has a circular disk-shaped cross-sectional area. However, the opening 310 can also have a different cross-sectional shape. The opening 310 has an opening diameter 311 in the lateral direction.

[0026] The photoresist layer 300 may comprise a positive resist. In this case, the photoresist of the photoresist layer 300 was exposed in the region of the opening 310. The exposed portions of the photoresist layer 300 were then removed.

[0027] Fig. 4 shows the semiconductor crystal 100 in a schematic sectional view in one of the representations of the Fig. 3 chronologically subsequent processing stage. The first layer 200 arranged on the surface 110 of the semiconductor crystal 100 has been partially removed. Preferably, the removal of the portion of the first layer 200 was carried out by wet-chemical etching. The wet-chemical etching medium attacked the first layer 200 through the opening 310 in the photoresist layer 300.

[0028] The partial removal of the first layer 200 creates an opening 210 in the first layer 200, accessible through the opening 310 in the photoresist layer 300, which exposes the surface 110 of the semiconductor crystal 100 in an exposed lateral region 120. In a coverage region 111, the surface 110 of the semiconductor crystal 100 continues to be covered by the first layer 200 even after the removal of part of the first layer 200. The lateral region 120 of the surface 110 of the semiconductor crystal 100 exposed by the opening 210 in the first layer 200 has an exposed diameter 123. The exposed diameter 123 is preferably larger than the opening diameter 311 of the opening 310 in the photoresist layer 300.In a projection perpendicular to the surface 110 of the semiconductor crystal 100, the centers of the opening 310 in the photoresist layer 300 and the center of the exposed lateral region 120 of the surface 110 of the semiconductor crystal 100 with the exposed diameter 123 preferably lie approximately on top of one another.

[0029] Since the diameter of the opening 210 in the first layer 200 is larger in the lateral direction than the opening diameter 311 of the opening 310 in the photoresist layer 300, an undercut 220 has been created under the photoresist layer 300. The photoresist layer 300 has thus been partially undercut during the partial removal of the first layer 200.

[0030] Fig. 5 shows the semiconductor crystal 100 in a schematic sectional view in one of the representations of the Fig. 4 chronologically subsequent processing stage. A metal layer 400 has been deposited from the side of the photoresist layer 300. The metal layer 400 is arranged on the side of the photoresist layer 300 facing away from the first layer 200. Material of the metal layer 400 has also reached the exposed lateral region 120 of the surface 110 of the semiconductor crystal 100 through the opening 310 in the photoresist layer 300 and has formed a contact area 410 there. The contact area 410 covers the exposed lateral region 120 of the surface 110 of the semiconductor crystal 100 in a contact region 121. The contact region 121 is arranged approximately centrally in the exposed lateral region 120 of the surface 110 of the semiconductor crystal 100 and is delimited externally by an annular or at least partially annular tolerance region 122 of the exposed lateral region 120.The tolerance region 122 of the exposed lateral region 120 is enclosed externally in a ring-shaped manner or at least in sections in a ring-shaped manner by the covering region 111 of the surface 110 of the semiconductor crystal 100.

[0031] The contact area 410 has a contact diameter 124 in the lateral direction, which is smaller than the exposed diameter 123. The contact diameter 124 of the contact area 410 corresponds approximately to the opening diameter 311 of the opening 310 in the photoresist layer 300. The opening diameter 311 of the opening 310 in the photoresist layer 300 thus determines the contact diameter 124 of the contact area 410.

[0032] The metal layer 400 comprises an electrically conductive material. For example, the metal layer 400 may comprise gold or silver. The metal layer 400 may also include an adhesion promoter such as platinum, titanium, or chromium, which is applied before the remaining metal layer 400 is applied to improve the adhesion of the metal layer 400.

[0033] The contact surface 410 formed from the metal layer 400 provides a good electrical connection to the semiconductor crystal 100. A specific contact resistance between the contact surface 410 and the semiconductor crystal 100 is preferably low.

[0034] The undercut 220 of the photoresist layer 300 ensures that the portion of the metal layer 400 disposed on the photoresist layer 300 is not connected to the portion of the metal layer 400 forming the contact surface 410. This enables the portion of the metal layer 400 disposed on the photoresist layer 300 to be lifted off using a lift-off process.

[0035] Fig. 6 shows the semiconductor crystal 100 in a schematic sectional view in one of the representations of the Fig. 5 chronologically subsequent processing stage. The photoresist layer 300 was removed together with the part of the metal layer 400 arranged on the photoresist layer 300. Thus, the first layer 200 with the opening 210 and the contact area 410 arranged in the contact region 121 of the exposed lateral region 120 of the surface 110 of the semiconductor crystal 100 remain on the surface 110 of the semiconductor crystal 100.

[0036] Fig. 7 shows the semiconductor crystal 100 in a schematic sectional view in one of the representations of the Fig. 6 temporally subsequent processing stage. A second layer 500 has been arranged on the surface 110 of the semiconductor crystal 100, the contact area 410, and the first layer 200. The second layer 500 covers the side of the first layer 200 facing away from the semiconductor crystal 100, the tolerance region 122 of the exposed lateral region 120 of the surface 110 of the semiconductor crystal 100, the contact area 410, and preferably also the wall of the opening 210 in the first layer 200.

[0037] The second layer 500 comprises a transparent, electrically conductive material. For example, the second layer 500 may comprise a transparent, electrically conductive oxide such as doped zinc oxide, indium zinc oxide, or indium tin oxide. The transparent, conductive material is transparent in an electromagnetic wavelength range that includes a wavelength of electromagnetic radiation emitted by the optoelectronic component made from the semiconductor crystal 100. The transparent, conductive material may, for example, have an absorption coefficient of 1000 per centimeter.

[0038] The material of the second layer 500 barely connects electrically to the semiconductor crystal 100 within the tolerance range 122 of the surface 110 of the semiconductor crystal 100. A specific contact resistance between the second layer 500 and the semiconductor crystal 100 is preferably very high. The specific contact resistance between the second layer 500 and the semiconductor crystal 100 is at least one order of magnitude higher than the specific contact resistance between the contact surface 410 and the semiconductor crystal 100. A highly electrically conductive connection exists between the contact surface 410 and the second layer 500.

[0039] Fig. Figure 8 shows the semiconductor crystal 100 in a schematic representation in one of the representations of the Fig. 7 chronologically subsequent processing stage. A third layer 600 was applied to the second layer 500. The third layer 600 serves as a mirror layer and preferably comprises a metal. For example, the third layer 600 can comprise gold or silver. The second layer 500 arranged between the first layer 200 and the third layer 600 can serve as an adhesion promoter for the third layer 600.

[0040] The third layer 600 is electrically connected to the contact surface 410 via the second layer 500. The third layer 600 can serve to provide an electrical contact to the contact surface 410 in an optoelectronic component made from the semiconductor crystal 100.

[0041] Fig. 9 shows the semiconductor crystal 100 in a schematic sectional view in one of the representations of the Fig. 8 subsequent processing status. In Fig. In the processing stage shown in Figure 9, the semiconductor crystal 100 is part of a largely completed optoelectronic component 10. The optoelectronic component 10 can, for example, be a light-emitting diode component. The semiconductor crystal 100 is then an LED chip.

[0042] A fourth layer 700 was applied to the third layer 600. The fourth layer 700 can serve as a connecting layer to a carrier or substrate of the optoelectronic component 10.

[0043] The optoelectronic component 10 can be electrically contacted via the third layer 600 and the contact area 410, as well as the intermediate second layer 500. The contact area 410 has the contact diameter 124, which is determined by the opening diameter 311 of the opening 310 of the photoresist layer 300, which can be reproducibly adjusted with high accuracy. Thus, the Fig.1 to 9, to reproducibly form the contact diameter 124 of the contact surface 410 with high precision. This results in good reproducibility of a forward voltage of the optoelectronic component 10. Since the second layer 500 is practically not electrically connected to the semiconductor crystal 100 in the tolerance range 122 of the exposed lateral region 120 of the surface 110 of the semiconductor crystal 100, the forward voltage is almost unaffected by the size of the tolerance range 122. The exposed diameter 123 of the lateral region 120 exposed when the opening 210 is created in the first layer 200 thus has virtually no influence on the forward voltage of the optoelectronic component 10.

[0044] During operation of the optoelectronic component 10, electromagnetic radiation, for example, visible light, is generated in the semiconductor crystal 100. Electromagnetic radiation leaving the semiconductor crystal 100 through the surface 110 is reflected back into the semiconductor crystal 100 by the first layer 200 and the third layer 600 to increase the light yield of the optoelectronic component 10.

[0045] In the region of the contact surface 410, electromagnetic radiation emerging from the semiconductor crystal 100 is at least partially absorbed by the first surface 110.

[0046] Since hardly any adjustment tolerances have to be taken into account when forming the contact surface 410, the contact diameter 124 of the contact surface 410 can be selected to be comparatively small, so that the proportion of electromagnetic radiation absorbed at the contact surface 410 is low overall.

[0047] Electromagnetic radiation emerging from the semiconductor crystal 100 in the tolerance range 122 of the exposed lateral region 120 of the surface 110 is absorbed to a significantly lesser extent than in the region of the contact surface 410. Electromagnetic radiation emerging from the semiconductor crystal 100 in the tolerance range 122 of the exposed lateral region 120 of the surface 110 is also essentially reflected back into the semiconductor crystal 100 by the third layer 600. As a result, the achievable light yield of the optoelectronic component 10 is largely independent of the size of the tolerance range 122 and thus also of the exposed diameter 123 of the exposed lateral region 120. List of reference symbols 10 optoelectronic component 100 semiconductor crystals 110 Surface 111 Coverage area (third lateral area) 120 exposed lateral area 121 Contact area (first lateral area) 122 Tolerance range (second lateral range) 123 exposed diameter 124 contact diameter 200 first layer (dielectric) 210 Opening 220 undercut 300 photoresist layers 310 Opening 311 opening diameter 400 metal layer 410 contact surface 500 second layer (TLM) 600 third layer (mirror metal) 700 fourth layer (connection layer)

Claims

[1] Method for producing an optoelectronic component (10) comprising the following steps: - providing a semiconductor crystal (100) having a surface (110); - applying a first layer (200) comprising a dielectric to the surface (110); - applying and structuring a photoresist layer (300) on the first layer (200), wherein the photoresist layer (300) is structured such that it has an opening (310); - Partially removing the first layer to expose a first and a second lateral region (120, 121, 122) of the surface (110), wherein in a third lateral region (11) the first layer (200) is arranged on the surface, wherein the photoresist layer (300) is partially undercut during the removal of the first layer (200); - applying a contact surface (410) comprising a first metal in the first lateral region (121) of the surface (110); - removing the photoresist layer (300); - applying a second layer (500) comprising an optically transparent, electrically conductive material to the contact surface (410) and the second lateral region (120, 122) of the surface (110); - applying a third layer (600) comprising a second metal to the second layer (500). [2] The method according to claim 1, wherein the photoresist layer (300) comprises a positive resist. [3] Method according to one of the preceding claims, wherein the partial removal of the first layer (200) is carried out by wet chemical etching. [4] Method according to one of the preceding claims, wherein during the under-etching of the photoresist layer (300), a side of the photoresist layer (300) facing the semiconductor crystal (100) is partially exposed. [5] Method according to one of the preceding claims, wherein the exposed first and second lateral regions (120, 121, 122) of the surface (110) of the semiconductor crystal (100) have an exposed diameter (123) that is larger than an opening diameter (311) of the photoresist layer (300). [6] Method according to the preceding claim, wherein the contact surface (410) has a contact diameter (124) and the contact diameter (124) is less than the exposed diameter (123). [7] Method according to one of the preceding claims, wherein the diameter of the opening (210) in the first layer (200) directly at the semiconductor crystal (100) is smaller than the diameter of the opening (210) in the first layer (200) directly at the photoresist layer (300). [8] Method according to one of the preceding claims, wherein the second lateral region (122) is covered by the photoresist layer (300) during application of the contact surface (410). [9] Optoelectronic component (10) with a semiconductor crystal (100) having a surface (110) having a first lateral region (121), a second lateral region (122) and a third lateral region (111), wherein in the first lateral region (121) a contact surface (410) is arranged on the surface (110) which has a first metal, wherein in the third lateral region (111) a first layer (200) is arranged on the surface (110) which has a dielectric, wherein a second layer (500) comprising an optically transparent, electrically conductive material is arranged on the contact surface (410), the first layer (200) and the second lateral region (122) of the surface (110), wherein a third layer (600) comprising a second metal is arranged on the second layer (500), and wherein the second lateral region (122) is free from the contact surface (410) and the first layer (200). [10] Optoelectronic component (10) according to the preceding claim, wherein a diameter of an opening (210) in the first layer (200) becomes larger with increasing distance from the semiconductor crystal (100). [11] Optoelectronic component (10) according to one of claims 9 or 10, wherein the second lateral region (122) surrounds the first lateral region (121) at least in sections in an annular manner, and the third lateral region (111) surrounds the second lateral region (122) at least in sections in an annular manner.

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