Semiconductor device

Abstract

Device containing: a first reflective structure (108) containing first doped layers of a semiconductor material, wherein alternating first doped layers are doped with a p-doper; a second reflective structure (112) containing second doped layers of the semiconductor material, wherein alternating of the second doped layers are doped with an n dopant; an emitting semiconductor region (110) located between the first reflecting structure (108) and the second reflecting structure (112); a contact pad (114) on the second reflective structure (112), wherein the work function of the contact pad (114) is lower than the work function of the second reflective structure (112); a bonding layer (126) on the contact pad (114), wherein the work function of the bonding layer (126) is higher than the work function of the second reflective structure (112); a conductive connector (210) on the bonding layer (126); a structure (200) comprising an integrated circuit or an interposer, and having a second contact pad (208), wherein the second contact pad (208) and the conductive connector (210) are connected; and a passivation layer (304) which conformally extends along sides of the second contact pad (208) and the conductive connector (210).

Description

Claiming priority and cross-references

[0001] This application claims priority over the preliminary US patent application No. 62 / 694 759, filed on July 6, 2018, which is hereby incorporated by reference. BACKGROUND

[0002] The semiconductor industry has experienced rapid growth due to continuous improvements in the integration density of a wide variety of electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). These improvements in integration density have largely stemmed from repeated reductions in the minimum feature size, allowing more components to be integrated into a given area. Optical components have been increasingly integrated into semiconductor devices in recent years, particularly due to the growing demand for cameras in phones, tablets, and other portable devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Aspects of this disclosure are best understood from the following detailed description when read in conjunction with the accompanying drawings. Note that, in accordance with industry practice, several features are not drawn to scale. In fact, the dimensions of the various features may be enlarged or reduced as desired for clarity of description. The Fig. Figures 1 to 7 show different cross-sectional views of a process for forming laser devices according to some embodiments. The Fig. Figures 8 to 21 show various cross-sectional views of a process for forming a laser device package according to some embodiments. Fig. Figure 22 shows the operation of a laser device package according to some embodiments. DETAILED DESCRIPTION

[0004] The following disclosure provides many different embodiments or examples for implementing various features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, only examples and are not intended to be limiting. For instance, forming a first feature over or on top of a second feature in the following description may include embodiments in which the first and second features are in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, so that the first and second features need not be in direct contact. Additionally, the present disclosure may repeat reference numerals and / or letters in the various examples.This repetition serves the purpose of simplicity and clarity and does not in itself imply any relationship between the various described embodiments and / or configurations.

[0005] Furthermore, spatially relative terms such as "below," "under," "lower," "above," "upper," and similar terms can be used here for the sake of simplicity to describe the relationship of one element or feature to one or more other elements or features, as shown in the figures. These spatially relative terms are intended to encompass various orientations of the device being used or operated, in addition to the orientation shown in the figures. The device may be oriented differently (rotated by 90 degrees or in another orientation), and the spatially relative terms used here may be interpreted accordingly.

[0006] In some embodiments, laser devices are configured with contact pads. The laser diodes of the laser devices are PIN diodes made of a doped semiconductor material such as doped GaAs. The contact pads and the semiconductor material share an ohmic junction. Under-bump metallurgies (UBMs) are formed on the contact pads before conductive connectors are electrically coupled to the laser devices. The UBMs help prevent metal interdiffusion between the contact pads and the conductive connectors. When the conductive connectors are melted, the junction between the contact pads and the semiconductor material retains its ohmic properties. Thus, low-resistance electrical connections can be established for the laser devices.

[0007] The Fig. Figures 1 to 7 show various cross-sectional views of a process for forming laser devices according to some embodiments. A first structure 100 is formed, comprising a support substrate 102 with a plurality of laser devices 104 formed thereon (see Figure 1). Fig. 7) contains. The laser devices 104 contain single-frequency laser diodes. In the embodiment shown, the laser devices 104 contain surface-emitting laser devices with a vertical resonator. It is understood that the laser devices 104 may contain other types of diodes, such as distributed Bragg reflector (DBR) laser diodes, light-emitting diodes (LEDs), or the like.

[0008] In Fig. 1. A support substrate 102 is provided. The support substrate 102 can be a semiconductor substrate, for example, a bulk semiconductor, a semiconductor-on-insulator (SOI) substrate, or the like, which may be doped (e.g., with a p- or n-type dopant) or undoped. The support substrate 102 can be a wafer, for example, a silicon wafer. In general, an SOI substrate consists of a layer of semiconductor material formed on an insulating layer. The insulating layer may be, for example, a buried oxide (BOX) layer, a silicon oxide layer, or the like. The insulating layer is provided on a substrate, usually a silicon or glass substrate. Other substrates may also be used, for example, a multilayer or gradient substrate.In some embodiments, the semiconductor material of the support substrate 102 can comprise silicon; germanium; a compound semiconductor such as silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide and / or indium antimonide; an alloy semiconductor such as SiGe, GaAs, GaAsAl, GaAsP, GaN, InGaP, AlAs, InP, GaP, InGaN and / or InAlN; or combinations thereof. In a particular embodiment, the support substrate 102 is a GaAs substrate.

[0009] Furthermore, one or more etch stop layers 106 are formed on the support substrate 102. In some embodiments, the one or more etch stop layers 106 are formed from a dielectric such as silicon carbide, silicon nitride, silicon oxynitride, or the like. In some embodiments, the one or more etch stop layers 106 are formed from a semiconductor material such as InGaP, InP, GaAsAl, AlAs, or the like. The one or more etch stop layers 106 are selective for an etching process used to structure subsequently formed reflective structures (see below), so that the support substrate 102 can be protected during the etching process.

[0010] Furthermore, a first reflective structure 108 is formed on one or more etch stop layers 106. The first reflective structure 108 contains several material layers, such as dielectric or semiconductor materials. The layers can be doped or undoped. The layers can be deposited by a suitable deposition process such as chemical vapor deposition (CVD) or can be grown by a suitable epitaxial process. The first reflective structure 108 can be a distributed Bragg reflector that uses alternating layers of materials with different refractive indices to reflect light. In some embodiments, the first reflective structure 108 contains alternating doped and undoped layers of the support substrate material 102 (e.g., GaAs), wherein the doped layers have different refractive indices than the undoped layers.The dopant can be any dopant that allows the doped layers to have different refractive indices than the undoped layers. In some embodiments, the dopant is a p-type dopant such as carbon. In some embodiments, the doped layers of the first reflective structure 108 have a doping concentration in the range of about 1E15 atoms / cm. 3 up to about 1E21 atoms / cm² 3 The first reflective structure 108 can thus form p-type reflective regions in the resulting laser diodes.

[0011] Furthermore, an emitting semiconductor region 110 is formed on the first reflective structure 108. The emitting semiconductor region 110 also contains a doped layer of the substrate material 102 (e.g., GaAs). The emitting semiconductor junction 110 has a p-region and an n-region and forms a pn junction that lasers at a single resonant frequency during operation. The p-region can be doped with p-type dopants such as boron, aluminum, gallium, indium, and the like. The n-region can be doped with n-type dopants such as phosphorus, arsenic, and the like. In some embodiments, the p-region is formed above the n-region. The n-region of the emitting semiconductor region 110 can be connected to the first reflective structure 108 such that light is emitted in the direction of the first reflective structure 108.

[0012] Furthermore, a second reflective structure 112 is formed on the emitting semiconductor region 110. The p-region of the emitting semiconductor region 110 can be connected to the second reflective structure 112. The second reflective structure 112 contains several layers of material, such as dielectric or semiconductor materials. The layers can be doped or undoped. The layers can be deposited by a suitable deposition process such as CVD or can be grown by a suitable epitaxial process. The second reflective structure 112 can be a distributed Bragg reflector that uses alternating layers of materials with different refractive indices to reflect light. In some embodiments, the second reflective structure 112 contains alternating doped and undoped layers of the support substrate material 102 (e.g.,GaAs), wherein the doped layers have different refractive indices than the undoped layers. The dopant can be any dopant that allows the doped layers to have different refractive indices than the undoped layers. In some embodiments, the dopant is an n-type dopant such as silicon. In some embodiments, the doped layers of the second reflective structure 112 have a doping concentration in the range of about 1E15 atoms / cm. 3 up to about 1E21 atoms / cm² 3 The second reflective structure 112 can thus form reflective n-regions in the resulting laser diodes. The dopant of the second reflective structure 112 can be a different dopant than the dopant of the first reflective structure 108.

[0013] The reflective structures 108 and 112 form a resonant cavity that helps to increase the intensity of the light from the emitting semiconductor region 110. The reflective structures 108 and 112 have different reflectivities; for example, their refractive indices differ. In some embodiments, the first reflective structure 108 is configured to have a lower reflectivity than the second reflective structure 112 to facilitate the emission of a laser beam from the emitting semiconductor region 110. The refractive indices of the reflective structures 108 and 112 can be varied by adjusting their overall height and total doping. For example, the height H1 of the first reflective structure 108 can be smaller than the height H2 of the second reflective structure 112.In some embodiments, the height H1 is in the range of about 1 µm to about 5 µm (such as about 3 µm) and the height H2 is in the range of about 1 µm to about 8 µm (such as about 6 µm).

[0014] In Fig. 2. Contact pads 114 are formed on the second reflective structure 112. The contact pads 114 are spatially and electrically connected to the second reflective structure 112, which itself is spatially and electrically connected to the emitting semiconductor region 110. The contact pads 114 are thus connected to the n-side of the laser diodes. The contact pads 114 can be a single layer or a composite layer containing several sublayers (shown with a dashed line) formed from different materials. In some embodiments, the contact pads 114 are formed from Ge, Au, GeAu, Ni, Ti, Ta, Pt, Cu, Al, W, In, Ag, Sn, Zn, Pd, Mn, Sb, Be, Mg, Si, or the like, or combinations thereof. In embodiments in which the second reflective structure 112 is formed from n-doped GaAs, the contact pads 114 may contain at least one layer of Au, GeAu or Ni.For example, the contact pads 114 can be a single layer of Au, GeAu, or Ni, or a composite layer, wherein the bottommost sublayer is an Au, GeAu, or Ni sublayer and the one or more upper layers are one or more other conductive materials. The contact pads 114 can be configured with any desired width W1. In some embodiments, the width W1 is in the range of about 8 µm to about 28 µm (such as about 12 µm).

[0015] As an example of forming the contact pads 114, a photoresist is formed and patterned over the second reflective structure 112. The photoresist can be formed by rotoplating or similar processes and exposed to light for patterning. The structure of the photoresist corresponds to the contact pads 114. The patterning creates openings through the photoresist to expose areas of the second reflective structure 112. A conductive material is formed in the openings of the photoresist and on the exposed sections of the second reflective structure 112. The conductive material can be formed by a deposition process such as physical vapor deposition (PVD), electron beam PVD, or similar processes. The photoresist and excess conductive material are then removed.The photoresist and the excess portions of the conductive material can be removed by a suitable lifting process, for example by ashing with an oxygen plasma or the like.

[0016] The contact pads 114 are referred to as ohmic contacts for the laser diodes. An ohmic contact for a semiconductor material is a contact that shares an ohmic metal-semiconductor junction with the semiconductor material. An ohmic metal-semiconductor junction exhibits a constant current-to-voltage ratio during operation. The materials of the second reflective structure 112 and the contact pads 114 (especially their work function) determine whether their metal-semiconductor junction is an ohmic junction or a Schottky junction. If the work function of the metal (e.g., the contact pads 114) is lower than the work function of the semiconductor material (e.g., the second reflective structure 112), the junction is an ohmic junction. If the work function of the metal (e.g., of the contact pads 114) is higher than the work function of the semiconductor material (e.g., of the second reflective structure 112), the junction is a Schottky junction.The work function of one or more materials of the contact pads 114 is lower than the work function of one or more materials of the second reflective structure 112.

[0017] In Fig. 3. Passivation features 116 are formed on the contact pads 114 and the second reflective structure 112. The passivation features 116 protect the contact pads 114 and act as an etching mask during subsequent processing. The passivation features 116 can be formed with any desired width W2. In some embodiments, the width W2 is in the range of about 10 µm to about 30 µm (such as about 13 µm). As an example of forming the passivation features 116, a hard mask layer is formed on the contact pads 114 and the second reflective structure 112. The hard mask layer can be formed from an inorganic material, which may be a nitride (such as silicon nitride), an oxide (such as silicon oxide or aluminum oxide), or the like, or combinations thereof, and can be formed by a deposition process such as CVD, atomic layer deposition (ALD), or the like.In some embodiments, the hard mask layer is an oxide. A photoresist is then formed and patterned on the hard mask layer. The photoresist can be formed by spin coating or the like and exposed to light for patterning. The pattern of the photoresist corresponds to the passivation features 116. The patterning creates openings through the photoresist. The patterned photoresist is then used in an etching process, such as anisotropic wet or dry etching, to pattern the hard mask layer, with remaining portions of the hard mask layer forming the passivation features 116. The photoresist can then be removed by a suitable ashing or stripping process, for example, using an oxygen plasma or the like.

[0018] In Fig. In step 4, openings 118 are formed in the second reflective structure 112, the emitting semiconductor region 110, and the first reflective structure 108. The remaining mesas are designated as laser diodes 120. The laser diodes 120 are PIN diodes. The openings 118 can be formed by a suitable etching process, for example, using anisotropic dry etching. The passivation features 116 are used as a mask during the etching process, and the one or more etch stop layers 106 are used to stop the etching process. A cleaning process can be performed to remove excess material after the etching process. For example, wet etching using dilute high-fluorescence (dHF) acid can be performed to remove excess material.

[0019] The laser diodes 120 are spaced apart by a distance D1, which is determined by the width of the openings 118. In some embodiments, the distance D1 is in the range of approximately 4 µm to approximately 100 µm. Furthermore, the laser diodes 120 are designed with a tapered shape. Lower sections of the first reflecting structures 108 have a lower width W L on, and upper sections of the second reflecting structures 112 have an upper width W U on. In some embodiments, the lower width W L in the range of approximately 10 µm to approximately 30 µm (such as approximately 14 µm), and the upper width W U lies in the range of 12 µm to approximately 32 µm.

[0020] In Fig. 5. Protective spacers 122 are formed on the sides of the laser diodes 120. The protective spacers 122 can be made of a dielectric such as SiN or SiO₂. xThe protective spacers 122 may be formed from Al2O3, AlN, a combination thereof, or the like. They can be formed by conformal deposition followed by anisotropic etching. For example, a deposition process such as CVD, ALD, or the like can be used to deposit the protective spacers 122.

[0021] Furthermore, opaque sections 110B are formed in the emitting semiconductor regions 110. The opaque sections 110B are located on the sides of the laser diodes 120; for example, in a top view, the opaque sections 110B extend around the perimeter of the transparent sections 110A of the emitting semiconductor regions 110. The opaque sections 110B essentially block or absorb light from the emitting semiconductor region 110, so that the light is not emitted laterally by the resulting laser diodes (e.g., in a direction parallel to a major surface of the support substrate 102). The opaque sections 110B and the reflective structures 108 and 112 form the resonant cavity of the laser diodes 120.The opaque sections 110B are oxidized material of the emitting semiconductor regions 110 and can be formed by an oxidation process such as a rapid thermal oxidation (RTO) process, a chemical oxidation process, rapid annealing (RTA) carried out in an oxygen-containing environment, or the like.

[0022] In Fig. 6. The passivation features 116 are structured with openings 124 that expose the contact pads 114. The structuring can be carried out by a suitable process, for example, by an etching process if the passivation features 116 are an oxide material. For example, a photoresist can be formed and structured on the passivation features 116. The photoresist can be formed by spin coating or the like and exposed to light for structuring. The structure of the photoresist corresponds to the passivation features 116. The structuring forms openings through the photoresist. The structured photoresist is then used in an etching process, such as anisotropic wet or dry etching, to form the openings 124 through the passivation features 116, thereby exposing the contact pads 114. The openings 124 can be formed with any width W3.In some embodiments, the width W3 is in the range of approximately 6 µm to approximately 26 µm (such as approximately 11 µm). The photoresist can then be removed by a suitable ashing or stripping process, for example using an oxygen plasma or the like.

[0023] In Fig. 7. UBMs 126 are formed in the openings 124 of the passivation features 116. The UBMs 126 can be referred to as bonding metal layers or simply as bonding layers and are spatially and electrically connected to the contact pads 114. The UBMs 126 can be a single layer or a composite layer containing several sublayers (shown with a dashed line) formed from different materials. In some embodiments, the UBMs 126 are formed from Ti, Ta, Ni, Cu, Sn, In, Au, Al, Pt, Pd, Ag, combinations thereof, or the like. In embodiments in which the contact pads 114 are formed from Au, GeAu, or Ni, the UBMs 126 can contain at least one Ti layer.For example, the UBMs 126 can be a single layer of Ti or a composite layer, wherein the bottommost sublayer is a Ti sublayer and the one or more upper layers are one or more other conductive materials. The UBMs 126 can be configured with any width W4. In some embodiments, the width W4 is in the range of approximately 8 µm to approximately 28 µm (such as approximately 12 µm).

[0024] As an example of forming the UBMs 126, a photoresist is formed and patterned over the passivation features 116 and in the openings 118 and 124. The photoresist can be formed by spin coating or similar processes and exposed to light for patterning. The structure of the photoresist corresponds to the UBMs 126. The patterning creates openings through the photoresist to expose the contact pads 114. A conductive material is formed in the openings of the photoresist and on the exposed portions of the contact pads 114. The conductive material can be formed by a deposition process such as PVD, electron beam PVD, or similar. Then, the photoresist and excess conductive material are removed.The photoresist and the excess portions of the conductive material can be removed by a suitable lifting process, for example by ashing with an oxygen plasma or the like.

[0025] The UBMs 126 are formed from one or more different materials than the contact pads 114. In subsequent processing, conductive connectors such as solder connectors are formed and connected to the UBMs 126. The UBMs 126 act as protective layers in the subsequent melting processes, preventing metal interdiffusion with the contact pads 114. The UBMs 126 are formed from a material that would form a Schottky junction if it were formed directly on the second reflective structure 112. In other words, the work function of the UBMs 126 is higher than the work function of the contact pads 114 and is also higher than the work function of the second reflective structure 112.Since the contact pads 114 and the UBMs 126 share a metal-to-metal interface, no barrier is formed at the connection due to differences in the efflux efficiencies of their one or more materials.

[0026] Fig. Figure 8 shows a cross-sectional view of a second structure 200 according to some embodiments. The second structure 200 can be a device such as an integrated circuit, an interposer, or the like. The second structure 200 contains a semiconductor substrate 202 with devices such as transistors, diodes, capacitors, resistors, etc., formed in and / or on the semiconductor substrate 202. The devices can be interconnected by an interconnection structure 204, which is formed, for example, by metallization structures in one or more dielectric layers on the semiconductor substrate, so that they form an integrated circuit. The metallization structures of the interconnection structure 204 include pads 204A and 204B, which can be used for connecting to the cathodes and anodes of the laser diodes, respectively. The metallization structures can be made of Cu, Al, or the like.A passivation layer 206 is formed over the interconnect structure 204 to protect the structure. The passivation layer 206 can be made of one or more suitable dielectrics such as silicon oxide, silicon nitride, low-k dielectrics such as carbon-doped oxides, extremely low-k dielectrics such as porous carbon-doped silicon dioxide, a polymer such as polyimide, solder mask, polybenzoxazole (PBO), benzocyclobutene (BCB), molding compound, the like, or a combination thereof.

[0027] The second structure 200 further comprises contact pads 208, such as aluminum or copper pads or pillars, with which external connections are established. The contact pads 208 are located on so-called active sides of the second structure 200 and can be formed, for example, by photolithography, etching, and plating processes such that they extend through the passivation layer 206. The contact pads 208 can be made of a conductive material such as Cu, Ni, Ti, or the like. In some embodiments, the contact pads 208 are multilayered; for example, the contact pads 208 comprise a copper layer on a nickel layer, with the copper layer and the nickel layer each being approximately 1 µm thick.

[0028] Conductive connectors 210 are formed on the contact pads 208. The conductive connectors 210 can be made of a conductive material such as solder, copper, aluminum, gold, nickel, silver, palladium, tin, bismuth, or a combination thereof. In some embodiments, the conductive connectors 210 are solder joints, such as lead-free solder. In some embodiments, the conductive connectors 210 are formed by first forming a solder layer on the contact pads 208 by processes such as vapor deposition, electroplating, printing, solder transfer, bead placement, or the like. After a solder layer has been formed on the contact pads 208, melting can be performed to shape the material into desired bump shapes. The conductive connectors 210 can have any height. In some embodiments, the conductive connectors 210 have a height of approximately 3 µm.

[0029] The Fig. Figures 9 to 21 show various cross-sectional views of a process for forming a laser device package 300 according to some embodiments. The laser device package 300 can be further processed by combining it with a detector to form, for example, an image sensor, a fiber optic network device, or the like. The resulting device can be part of an integrated circuit device, such as a system-on-chip (SoC).

[0030] In Fig. In step 9, the first structure 100 is connected to the second structure 200. After the laser devices 104 are attached, the laser devices 104, the conductive connectors 210, and parts of the contact pads 208 above the passivation layer 206 have a combined height H3. In some embodiments, the combined height H3 is in the range of about 3 µm to about 35 µm (such as about 14 µm).

[0031] The laser devices 104 of the first structure 100 are connected to the contact pads 208 of the second structure 200 by the conductive connectors 210. The conductive connectors 210 can be brought into contact with the UBMs 126, and a melting process can be performed to spatially and electrically connect the UBMs 126 and the conductive connectors 210. The UBMs 126 act as protective layers during the melting process and prevent metal interdiffusion between the conductive connectors 210 and the contact pads 114. As a result, less metal interdiffusion occurs at the interface 104A of the UBMs 126 and the contact pads 114 during the melting process than at the interface 104B of the UBMs 126 and the conductive connectors 210. In some embodiments, an intermetallic compound (IMC) can be formed at interface 104B, but essentially no IMCs need to be formed at interface 104A (e.g.The interface between the UBMs 126 and the contact pads 114 can be essentially free of IMCs. By avoiding metal interdiffusion with the contact pads 114, the interfaces between the contact pads 114 and the second reflective structure 112 retain their ohmic properties. In other words, the work function of one or more of the materials of the contact pads 114 is the same before and after melting.

[0032] When the first structure 100 is connected to the second structure 200, the second reflecting structures 112 (e.g., the n-sides or cathodes) of the laser devices 104 face the second structure 200, and the first reflecting structures 108 (e.g., the p-sides or anodes) of the laser devices 104 face the support substrate 102. Thus, the cathodes of the laser devices 104 are connected to the pads 204A of the interconnecting structure 204. As mentioned above, the first reflecting structures 108 have a lower reflectivity than the second reflecting structures 112. Therefore, the laser beam generated by the emitting semiconductor region 110 is reflected by the second reflecting structures 112. Part of the reflected laser beam is further reflected by the first reflecting structure 108, and part is transmitted through the first reflecting structure 108.

[0033] After the first structure 100 is joined to the second structure 200, a backing 302 can be formed between the structures. The backing 302 can be made of a molding compound, an epoxy resin, or the like. The backing 302 does not need to be cured and is used as a temporary support for the second structure 200 during subsequent processing. If the backing 302 is not cured, it can be more easily removed once the subsequent processing is complete.

[0034] In Fig. In step 10, the support substrate 102 is removed, leaving behind the laser devices 104 and the one or more etch stop layers 106. The support substrate 102 can be removed by an etching process, such as wet etching, which is selective for the material of the support substrate 102 (e.g., GaAs). The one or more etch stop layers 106 can halt the etching process. The underfill 302 supports the one or more etch stop layers 106 and prevents them from collapsing during the removal of the support substrate 102.

[0035] In Fig. In step 11, one or more etch stop layers 106 are removed, leaving behind the laser devices 104. The one or more etch stop layers 106 can be removed by an etching process such as wet etching, which is selective for the material of the support substrate 102 (e.g., GaAs). The underfill 302 is also removed, e.g., by an etching process such as wet or dry etching. After the removal processes, the laser devices 104 remain.

[0036] In Fig. In the embodiment 12, a passivation layer 304 is formed over the laser devices 104 and the passivation layer 206. The passivation layer 304 also extends along the sides of the contact pads 208 and the conductive connectors 210. The passivation layer 304 can be made of silicon oxide, silicon nitride, or the like, and can be formed by a deposition process such as CVD, ALD, or the like. In some embodiments, the passivation layer 304 is made of an oxide (such as silicon oxide) and is formed by ALD. The passivation layer 304 is formed with a thickness T1. In some embodiments, the thickness T1 is in the range of about 0.01 µm to about 0.5 µm.

[0037] Furthermore, an insulating material 306 is formed over the passivation layer 304. The insulating material 306 can be an oxide (such as silicon oxide), a polymer (such as a polyimide, a low-temperature polyimide (LTPI), PBO, or BCB), or the like. In embodiments where the insulating material 306 is an oxide, it can be formed by a deposition process such as CVD, ALD, or the like. In embodiments where the insulating material 306 is a polymer, it can be formed by a coating process such as rotational coating. The insulating material 306 is formed with a thickness T2 that is greater than the thickness T1 of the passivation layer 304. In some embodiments, the thickness T2 is in the range of about 3 µm to about 100 µm. The insulating material 306 surrounds and encases the laser devices 104.Parts of the insulating material 306 above the laser devices 104 have a thickness T3. In some embodiments, the thickness T3 is approximately 65 µm or less.

[0038] In Fig. 13 A planarization process is performed to planarize and thin the insulating material 306. In particular, the amount of insulating material 306 above the laser devices 104 is reduced. The planarization process can be, for example, a grinding process, a chemical-mechanical polishing (CMP) process, or the like. After planarization and thinning, portions of the insulating material 306 above the laser devices 104 have a reduced thickness T4, which is less than the thickness T3. In some embodiments, the reduced thickness T4 is less than or equal to approximately 5 µm (such as approximately 1 µm).

[0039] In Fig. 14. A mask layer 308 is formed on the insulating material 306. In some embodiments, the mask layer 308 is formed from a metal or a metal-containing material such as Ti, Cu, TiW, TaN, TiN, combinations thereof, or multiple layers thereof. In some embodiments, the mask layer 308 is formed from a dielectric such as SiC or the like. The mask layer 308 can be referred to as a hard mask layer. The mask layer 308 can be formed by a deposition process such as PVD, CVD, or the like.

[0040] In Fig. Openings 310 are formed in the mask layer 308, the insulating material 306, the passivation layer 304, and the passivation layer 206. The pads 204B of the interconnect structure 204 are exposed through the openings 310. The openings 310 can be formed by a two-stage etching process, wherein the mask layer 308 is patterned in a first etching process, and the pattern of the mask layer 308 is transferred to underlying features in a second etching process. As an example of the two-stage etching process, a photoresist is formed and patterned over the mask layer 308. The photoresist can be formed by spin coating or the like and exposed to light for patterning. The pattern of the photoresist corresponds to the openings 310. The mask layer 308 is patterned by transferring the pattern of the photoresist to the mask layer 308.The mask layer 308 can be structured by a suitable etching process, for example, wet etching, dry etching, or a combination thereof, using the structured photoresist as the etching mask. The insulating material 306, the passivation layer 304, and the passivation layer 206 are then structured by transferring the structure of the mask layer 308 to underlying features. In some embodiments, the mask layer 308 can be removed before subsequent processing. In the embodiment shown, the mask layer 308 remains and is removed after subsequent processing steps have been performed.

[0041] The openings 310 can be formed with any desired width W5. The two-stage etching process allows the width W5 of the openings 310 to have a small critical dimension. In some embodiments, the width W5 is in the range of approximately 1 µm to approximately 80 µm (such as approximately 3 µm). Furthermore, the openings 310 can be formed to any desired depth D2. In some embodiments, the depth D2 is in the range of approximately 3 µm to approximately 41 µm (such as approximately 14 µm). The two-stage etching process allows the depth-to-width ratio of the openings 310 to be large. In some embodiments, the depth-to-width ratio of the openings 310 is in the range of approximately 40:1 to approximately 2:1.

[0042] In Fig. In embodiment 16, a nucleation layer 312 is formed in the openings 310 and on the pads 204B of the interconnection structure 204. In embodiments where the mask layer 308 remains, the nucleation layer 312 also extends along the mask layer 308. The nucleation layer 312 is a metal layer that can be a single layer or a composite layer containing multiple sublayers formed from different materials. In some embodiments, the nucleation layer 312 includes a titanium layer and a copper layer over the titanium layer. The nucleation layer 312 can be formed by a deposition process such as PVD or the like. A barrier layer can also be formed over the nucleation layer 312. The barrier layer can be made of TaN, TiN, or the like and can be formed by a deposition process such as PVD or the like.

[0043] In Fig. 17. A conductive material 314 is formed on the nucleation layer 312 and in the openings 310. The conductive material 314 can be a metal such as copper, tungsten, aluminum, titanium, or the like. The conductive material 314 can be formed by plating, such as electroplating or electroless plating, or the like.

[0044] In Fig. In step 18, a planarization process is performed to planarize the conductive material 314 and the insulating material 306. The planarization process can be, for example, a grinding process, a CMP process, or the like. Remaining portions of the conductive material 314 and the nucleation layer 312 form conductive vias 316 in the openings 310. The conductive vias 316 are spatially and electrically connected to the pads 204B of the interconnection structure 204.

[0045] In Fig. 19. Openings 318 are formed in the insulating material 306 and the passivation layer 304, thereby exposing the laser devices 104. The openings 318 can be formed by suitable photolithography and etching techniques. For example, a photoresist can be formed and patterned over the insulating material 306. The photoresist can be formed by rotoplating or the like and exposed to light for patterning. The structure of the photoresist corresponds to the openings 318. The insulating material 306 and the passivation layer 304 are patterned by transferring the structure of the photoresist onto the insulating material 306 and the passivation layer 304. The openings 318 are shallower than the openings 310, so the use of an additional hard mask during etching can be avoided.The insulating material 306 and the passivation layer 304 can be structured by a suitable etching process, for example, dry etching, using the structured photoresist as an etching mask. The openings 318 can be formed with any desired width W6. In some embodiments, the width W6 is in the range of approximately 10 µm to approximately 30 µm (such as approximately 13 µm).

[0046] In Fig. Electrodes 320 are formed in the openings 318 and along the upper surface of the insulating material 306, thereby forming contacts for the first reflective structures 108 of the laser devices 104. The electrodes 320 not only serve as contacts for the first reflective structures 108 of the laser devices 104, but also connect the laser devices 104 to the conductive vias 316. Thus, the pads 204A of the interconnection structure 204 are electrically connected to the second reflective structures 112 (e.g., the cathodes) via the conductive connectors 210, and the pads 204B of the interconnection structure 204 are electrically connected to the first reflective structures 108 (e.g., the anodes) via the electrodes 320 and the conductive vias 316.

[0047] Like the contact pads 114, the electrodes 320 are formed from a material that allows the metal-semiconductor junction of the electrodes 320 and the first reflective structures 108 to be ohmic. The electrodes 320 can be a single layer or a composite layer containing several sublayers (shown with a dashed line) formed from different materials. In some embodiments, the electrodes 320 are formed from Ti, Pt, Au, Cu, Al, Ni, combinations thereof, or the like. In embodiments in which the first reflective structures 108 are formed from p-doped GaAs, the electrodes 320 can contain at least one Ti or Pt layer. For example, the electrodes 320 can be a single layer of Ti or Pt or a composite layer, wherein the bottom sublayer is a Ti or Pt sublayer and the upper layers are one or more other conductive materials.

[0048] As an example of forming the electrodes 320, a photoresist is formed and structured over the insulating material 306 and the laser devices 104. The photoresist can be formed by rotoplating or the like and exposed to light for structuring. The structure of the photoresist corresponds to the electrodes 320. The structuring creates openings through the photoresist to expose the first reflective structures 108. A conductive material is formed in the openings of the photoresist and on the exposed portions of the first reflective structures 108. The conductive material can be formed by a deposition process such as PVD, electron beam PVD, or the like. Then the photoresist and excess portions of the conductive material are removed.The photoresist and the excess portions of the conductive material can be removed by a suitable lifting process, for example by ashing with an oxygen plasma or the like.

[0049] In Fig. In 21, a passivation layer 322 is formed over the electrodes 320 and the insulating material 306. The passivation layer 322 can be made of silicon oxide, silicon nitride, or the like, and can be formed by a deposition process such as CVD. In some embodiments, the passivation layer 322 is formed from an oxide (such as silicon oxide).

[0050] Fig. Figure 22 shows the operation of the laser device package 300 according to some embodiments. The laser device package 300 can be used as a laser beam source for a depth sensor 400. One or more laser beams can be generated in pulses by the laser devices 104 of the laser device package 300 and can be received by a detector 402 after being reflected by a target 404. A revolution time for the one or more laser beams can be measured and used to calculate the distance between the depth sensor 400 and the target 404. The detector 402 can, for example, be a CMOS image sensor such as a photodiode. In some embodiments, the detector 402 is formed on the same substrate as the laser device package 300. For example, the detector 402 can be formed in the semiconductor substrate 202 of the second structure 200 (see Figure 22). Fig. 8).

[0051] Certain embodiments can offer specific advantages. By selecting a suitable material for the contact pads 114, the metal-semiconductor junction between the second reflective structure 112 and the contact pads 114 can be ohmic (or at least exhibit a lower Schottky barrier). By forming the UBMs 126 between the contact pads 114 and the conductive connectors 210, metal interdiffusion between the contact pads 114 and the conductive connectors 210 can be avoided. The junctions of the contact pads 114 and the second reflective structures 112 can thus retain their ohmic properties when the conductive connectors 210 are melted. The contact resistance of the contact pads 114 can therefore be reduced, and the quality and / or reliability of the resulting connection can be increased.

[0052] In one embodiment, a device comprises: a first reflective structure containing first doped layers of a semiconductor material, wherein alternating layers of the first doped layers are doped with a p-type dopant; a second reflective structure containing second doped layers of the semiconductor material, wherein alternating layers of the second doped layers are doped with an n-type dopant; an emitting semiconductor region arranged between the first reflective structure and the second reflective structure; a contact pad on the second reflective structure, wherein the work function of the contact pad is lower than the work function of the second reflective structure; a bonding layer on the contact pad, wherein the work function of the bonding layer is higher than the work function of the second reflective structure; and a conductive connector on the bonding layer.

[0053] In some embodiments, the device further comprises: a passivation feature on the second reflective structure and the contact pad, wherein the bonding layer extends through the passivation feature. In some embodiments of the device, the semiconductor material is GaAs. In some embodiments of the device, the contact pad is a single layer of Au, GeAu, or Ni. In some embodiments of the device, the contact pad comprises: a first sublayer on the second reflective structure, wherein the first sublayer is Au, GeAu, or Ni; and a second sublayer on the first sublayer, wherein the second sublayer is a different conductive material than the first sublayer. In some embodiments of the device, the bonding layer is a single layer of Ti.In some embodiments of the device, the bonding layer comprises: a first sublayer on the contact pad, wherein the first sublayer is Ti; and a second sublayer on the first sublayer, wherein the second sublayer is a different conductive material than the first sublayer. In some embodiments, the device further comprises: a connecting structure comprising a first pad and a second pad, wherein the first pad is connected to the conductive connector; a conductive via connected to the second pad; an electrode connecting the conductive via to the first reflective structure; and a passivation layer on the electrode. In some embodiments, the device further comprises: an insulating material surrounding the conductive via, the first reflective structure, and the second reflective structure, wherein the electrode is positioned on the insulating material.

[0054] In one embodiment, a method comprises: forming a first reflective structure on a substrate, wherein the first reflective structure contains first doped layers of a semiconductor material, with alternating first doped layers being doped with a p-type dopant; forming an emitting semiconductor region on the first reflective structure; forming a second reflective structure on the emitting semiconductor region, wherein the second reflective structure contains second doped layers of the semiconductor material, with alternating second doped layers being doped with an n-type dopant; depositing a contact pad on the second reflective structure, wherein the work function of the contact pad is lower than the work function of the second reflective structure;Deposition of a bonding layer on the contact pad, wherein the work function of the bonding layer is higher than the work function of the second reflective structure; formation of a conductive connector on the bonding layer; and melting of the conductive connector.

[0055] In some embodiments, the method further comprises: forming a passivation feature on the second reflective structure and the contact pad; and structuring an opening in the passivation feature, wherein the bonding layer is deposited in the opening. In some embodiments, the method further comprises: etching the second reflective structure, the emitting semiconductor region, and the first reflective structure using the passivation feature as an etch mask, wherein, after etching, portions of the second reflective structure, the emitting semiconductor region, and the first reflective structure remaining form a laser diode, the laser diode having an upper width and a lower width, the upper width being smaller than the lower width.In some embodiments, the method further comprises: oxidizing the laser diode, wherein the oxidation forms an opaque section of the emitting semiconductor area on sides of the laser diode.

[0056] In one embodiment, a method comprises: contacting a laser device with a conductive connector, wherein the laser device comprises: a laser diode with a doped semiconductor material, the laser diode having an anode and a cathode; a contact pad on the cathode of the laser diode, the contact pad and the laser diode having an ohmic junction; and a bonding layer on the contact pad, wherein the conductive connector is brought into contact with the bonding layer; melting the conductive connector, wherein during melting an intermetallic compound is formed at an interface between the bonding layer and the conductive connector and no intermetallic compounds are formed at an interface between the bonding layer and the contact pad; forming an insulating material around the laser device and the conductive connector;Forming a conductive via through the insulating material; and forming an electrode that connects the conductive via to the anode of the laser diode.

[0057] In some embodiments, the method further comprises: forming an underfill around the laser device after the laser device has been brought into contact with the conductive connector; and removing the underfill before forming the insulating material. In some embodiments of the method, forming the conductive via comprises: forming a mask layer on the insulating material; structuring the mask layer with a first opening; transferring the first opening of the mask layer to the insulating material; forming a conductive material in the first opening; and planarizing the conductive material and the insulating material, with the remaining portions of the conductive material forming the conductive via.In some embodiments of the method, forming the electrode comprises: forming an opening in the insulating material, wherein the opening exposes the anode of the laser diode; and depositing the electrode in the opening, along a top surface of the insulating material and along the conductive via. In some embodiments of the method, depositing the electrode comprises: depositing a single layer of Ti or Pt. In some embodiments of the method, depositing the electrode comprises: forming a first sublayer, wherein the first sublayer is Ti or Pt; and forming a second sublayer on top of the first sublayer, wherein the second sublayer is a different conductive material than the first sublayer. In some embodiments, the method further comprises: depositing a passivation layer on the electrode and the insulating material.

[0058] The foregoing describes features of several embodiments so that a person skilled in the art can better understand the aspects of the present disclosure. The person skilled in the art should recognize that they can easily use the present disclosure as a basis for designing or modifying further processes and structures to achieve the same objectives and / or realize the same advantages of the embodiments introduced herein. The person skilled in the art should also recognize that such equivalent designs do not deviate from the spirit and scope of protection of the present disclosure and that they can make various changes, substitutions, and modifications here without deviating from the spirit and scope of protection of the present disclosure. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 62 / 694 759

[0001]

Claims

[1] Device containing: a first reflective structure (108) containing first doped layers of a semiconductor material, wherein alternating first doped layers are doped with a p-doper; a second reflective structure (112) containing second doped layers of the semiconductor material, wherein alternating of the second doped layers are doped with an n dopant; an emitting semiconductor region (110) located between the first reflecting structure (108) and the second reflecting structure (112); a contact pad (114) on the second reflective structure (112), wherein the work function of the contact pad (114) is lower than the work function of the second reflective structure (112); a bonding layer (126) on the contact pad (114), wherein the work function of the bonding layer (126) is higher than the work function of the second reflective structure (112); a conductive connector (210) on the bonding layer (126); a structure (200) comprising an integrated circuit or an interposer, and having a second contact pad (208), wherein the second contact pad (208) and the conductive connector (210) are connected; and a passivation layer (304) which conformally extends along sides of the second contact pad (208) and the conductive connector (210). [2] Device according to claim 1, further comprising: a passivation feature (116) on the second reflective structure (112) and the contact pad (114), wherein the bonding layer (126) extends through the passivation feature (116). [3] Device according to claim 1 or 2, wherein the semiconductor material is GaAs. [4] Device according to claim 1 or 2, wherein the contact pad (114) contains Ge, Au, GeAu, Ni, Ti, Ta, Pt, Cu, Al, W, In, Ag, Sn, Zn, Pd, Mn, Sb, Be, Mg, Si or a combination thereof. [5] Device according to claim 4, wherein the contact pad (114) is made of Ge, Au, GeAu, Ni, Ti, Ta, Pt, Cu, Al, W, In, Ag, Sn, Zn, Pd, Mn, Sb, Be, Mg, Si or a combination thereof. [6] Device according to one of claims 1, 2, 4 or 5, wherein the bonding layer (126) is made of a different material than the contact pad (114), wherein the work function of the material of the bonding layer (126) is higher than the work function of the material of the contact pad (114), and wherein the bonding layer (126) contains Ti, Ta, Ni, Cu, Sn, In, Au, Al, Pt, Pd, Ag, or a combination thereof. [7] Device according to claim 6, wherein the bonding layer (126) is formed from Ti, Ta, Ni, Cu, Sn, In, Au, Al, Pt, Pd, Ag or a combination thereof. [8] Device according to one of the preceding claims, further comprising: a connection structure (204) comprising a first pad (204A) and a second pad (204B), wherein the first pad (204A) is connected to the conductive connector (210); a conductive via which (316) is connected to the second pad (204B); an electrode (320) connecting the conductive via (316) to the first reflective structure (108); and a passivation layer (322) on the electrode (320). [9] Device according to claim 8, further comprising: an insulating material (306) surrounding the conductive via (316), the first reflective structure (108) and the second reflective structure (112), wherein the electrode (320) is arranged on the insulating material (306). [10] Device according to claim 9, wherein the conductive via (316) is formed from a metal such as copper, tungsten, aluminium, titanium. [11] Device containing: a first reflective structure (108) containing first doped layers of a semiconductor material, wherein alternating first doped layers are doped with a p-doper; a second reflective structure (112) containing second doped layers of the semiconductor material, wherein alternating of the second doped layers are doped with an n dopant; an emitting semiconductor region (110) located between the first reflecting structure (108) and the second reflecting structure (112); a contact pad (114) on the second reflective structure (112), wherein the work function of the contact pad (114) is lower than the work function of the second reflective structure (112); a bonding layer (126) on the contact pad (114), wherein the work function of the bonding layer (126) is higher than the work function of the second reflective structure (112); and a conductive connector (210) on the bonding layer (126); wherein the contact pad (114) is formed from Ti, Ta, Al, W, In, Ag, Sn, Zn, Mn, Mg or a combination thereof. [12] Device according to claim 11, further comprising: a passivation feature (116) on the second reflective structure (112) and the contact pad (114), wherein the bonding layer (126) extends through the passivation feature (116). [13] Device according to claim 11 or 12, wherein the semiconductor material is GaAs. [14] Device according to any one of claims 11 to 13, wherein the bonding layer (126) contains Ni, Cu, Au, Pt, Pd or a combination thereof. [15] Device according to claim 14, wherein the bonding layer (126) is formed of Ni, Cu, Au, Pt, Pd, or a combination thereof. [16] Device according to any one of claims 11 to 15, further comprising: a connection structure (204) comprising a first pad (204A) and a second pad (204B), wherein the first pad (204A) is connected to the conductive connector (210); a conductive via which (316) is connected to the second pad (204B); an electrode (320) connecting the conductive via (316) to the first reflective structure (108); and a passivation layer (322) on the electrode (320). [17] Device according to claim 16, further comprising: an insulating material (306) surrounding the conductive via (316), the first reflective structure (108) and the second reflective structure (112), wherein the electrode (320) is arranged on the insulating material (306). [18] Device according to claim 17, wherein the conductive via (316) is formed from a metal such as copper, tungsten, aluminium, titanium. [19] Device containing: a first reflective structure (108) containing first doped layers of a semiconductor material, wherein alternating first doped layers are doped with a p-doper; a second reflective structure (112) containing second doped layers of the semiconductor material, wherein alternating of the second doped layers are doped with an n dopant; an emitting semiconductor region (110) located between the first reflecting structure (108) and the second reflecting structure (112); a contact pad (114) on the second reflective structure (112), wherein the work function of the contact pad (114) is lower than the work function of the second reflective structure (112); a bonding layer (126) on the contact pad (114), wherein the work function of the bonding layer (126) is higher than the work function of the second reflective structure (112); and a conductive connector (210) on the bonding layer (126); wherein the contact pad (114) contains Ta, In, Mn, Mg or a combination thereof. [20] Device according to claim 19, further comprising: a passivation feature (116) on the second reflective structure (112) and the contact pad (114), wherein the bonding layer (126) extends through the passivation feature (116). [21] Device according to claim 19 or 20, wherein the semiconductor material is GaAs. [22] Device according to one of claims 19 to 21, wherein the contact pad (114) is made of Ta, In, Mn, Mg or a combination thereof. [23] Device according to any one of claims 19 to 22, wherein the bonding layer (126) contains Ni, Cu, Au, Pt, Pd or a combination thereof. [24] Device according to claim 23, wherein the bonding layer (126) is formed of Ni, Cu, Au, Pt, Pd, or a combination thereof. [25] Device according to any one of claims 19 to 24, further comprising: a connection structure (204) comprising a first pad (204A) and a second pad (204B), wherein the first pad (204A) is connected to the conductive connector (210); a conductive via which (316) is connected to the second pad (204B); an electrode (320) connecting the conductive via (316) to the first reflective structure (108); and a passivation layer (322) on the electrode (320). [26] Device according to claim 25, further comprising: an insulating material (306) surrounding the conductive via (316), the first reflective structure (108) and the second reflective structure (112), wherein the electrode (320) is arranged on the insulating material (306). [27] Device according to claim 19, wherein the conductive via (316) is formed from a metal such as copper, tungsten, aluminium, titanium.

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