Surface emitting laser module, optical device, and surface emitting laser substrate

Abstract

A surface emitting laser module includes a base substrate; a surface emitting laser substrate mounted on the base substrate, the surface emitting laser substrate including a surface emitting laser element, and the surface emitting laser substrate has a first face facing the base substrate and a second face facing away from the base substrate; and an optical element facing the second face and including a structure configured to receive light emitted from the second face of the surface emitting laser element. The surface emitting laser element includes a first semiconductor layer, a second semiconductor layer, a first electrode disposed on the first face and connected to the first semiconductor layer, and a second electrode disposed on the first face and connected to the second semiconductor layer. The base substrate includes a third electrode connected to the first electrode and a fourth electrode connected to the second electrode.

Description

Technical Field

[0001] The present invention relates to a surface emitting laser module, an optical device and a surface emitting laser substrate. Background Art

[0002] A vertical cavity surface emitting laser (VCSEL) is a semiconductor laser that oscillates laser light in a direction perpendicular to the substrate. VCSELs have the characteristics of low threshold current, single longitudinal mode oscillation, and two-dimensional array arrangement. VCSELs are sometimes used in combination with microlens arrays.

[0003] Patent document 1 describes a device in which a surface of a laser table (VCSEL element) on which a VCSEL device is formed faces a microlens array, and the microlens array is mounted on the surface. In the photonic device, a plurality of electrode pads are provided on the surface on which the VCSEL element is formed, and each electrode pad is connected to one of the corresponding VCSEL elements. These plurality of electrode pads are provided outside the portion where the microlens array contacts the VCSEL device, and are connected to an IC package by wire bonding.

[0004] According to the device described in Patent Document 1, a microlens array can be integrated into a VCSEL device. Summary of the invention

[0005] Technical issues

[0006] However, even if there is a demand for reducing the size of a surface emitting laser substrate such as a VCSEL device, the structure described in Patent Document 1 cannot fully meet the demand for reducing the size.

[0007] An object of the present invention is to provide a surface emitting laser module, an optical device, and a surface emitting laser substrate, the sizes of which can be further reduced.

[0008] Solutions to technical problems

[0009] According to one aspect of the technology disclosed in the present invention, a surface emitting laser module includes a base substrate; a surface emitting laser substrate mounted on the base substrate, the surface emitting laser substrate including a surface emitting laser element, and the surface emitting laser substrate has a first face facing the base substrate and a second face facing away from the base substrate; and an optical element facing the second face and including a light emitted from the second face of the surface emitting laser element. The surface emitting laser element includes a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, a first electrode disposed on the first face and connected to the first semiconductor layer, and a second electrode disposed on the first face and connected to the second semiconductor layer. The base substrate has a third face facing the first face of the surface emitting laser substrate, and includes a third electrode disposed on the third face and connected to the first electrode and a fourth electrode disposed on the third face and connected to the second electrode.

[0010] Beneficial effects of the present invention

[0011] According to the technology of the present disclosure, the size of the surface emitting laser substrate can be further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a top view showing a surface emitting laser module according to a first embodiment;

[0013] Figure 2 is a sectional view showing a surface emitting laser module according to a first embodiment (part 1);

[0014] Figure 3 is a sectional view showing a surface emitting laser module according to the first embodiment (part 2);

[0015] Figure 4 Shown in an enlarged manner Figure 2 a cross-sectional view of a portion of;

[0016] Figure 5 Shown in an enlarged manner Figure 3 a cross-sectional view of a portion of;

[0017] Figure 6 is a bottom view showing a VCSEL chip according to the first embodiment;

[0018] Figure 7 is a top view showing a VCSEL chip according to the first embodiment;

[0019] Figure 8 is a bottom view showing the MLA according to the first embodiment;

[0020] Fig. 9 is a cross-sectional view showing an MLA according to a first embodiment;

[0021] Fig. 10A is a cross-sectional view (part 1) showing a method for forming a VCSEL chip according to a first embodiment;

[0022] Fig. 10B is a cross-sectional view (part 2) showing a method for forming a VCSEL chip according to the first embodiment;

[0023] Fig. 10C is a cross-sectional view (part 3) showing a method for forming a VCSEL chip according to the first embodiment;

[0024] Fig. 10D is a cross-sectional view (Part 4) showing a method for forming a VCSEL chip according to the first embodiment;

[0025] Fig.10E is a cross-sectional view showing a method for forming a VCSEL chip according to the first embodiment (Part 5);

[0026] Fig.10F is a cross-sectional view showing a method for forming a VCSEL chip according to the first embodiment (Part 6);

[0027] Figure 10G is a cross-sectional view showing a method for forming a VCSEL chip according to the first embodiment (Part 7);

[0028] Fig.11A is a cross-sectional view showing a method for forming a VCSEL chip according to the first embodiment (Part 8);

[0029] Fig. 11B is a cross-sectional view showing a method for forming a VCSEL chip according to the first embodiment (Part 9);

[0030] Fig. 11C is a cross-sectional view (part 10 ) for illustrating a method for forming a VCSEL chip according to the first embodiment;

[0031] Fig.11D is a cross-sectional view (Part 11) showing a method for forming a VCSEL chip according to the first embodiment;

[0032] Fig.11E is a cross-sectional view (part 12) showing a method for forming a VCSEL chip according to the first embodiment;

[0033] Fig.11F is a cross-sectional view (Part 13) showing a method for forming a VCSEL chip according to the first embodiment;

[0034] Fig.11G is a cross-sectional view (part 14) showing a method for forming a VCSEL chip according to the first embodiment;

[0035] Fig.12 is a cross-sectional view showing a surface emitting laser module according to a reference example;

[0036] Fig.13 is a top view showing a VCSEL chip according to a reference example;

[0037] Fig.14 is a bottom view showing a VCSEL chip according to a modification of the first embodiment;

[0038] Fig.15 is a top view showing a surface emitting laser module according to a second embodiment;

[0039] Fig.16 is a sectional view showing a surface emitting laser module according to a second embodiment;

[0040] Fig.17 Shown in an enlarged manner Fig.16 a cross-sectional view of a portion of;

[0041] Fig.18 is a sectional view showing a surface emitting laser module according to a modification of the second embodiment; and

[0042] Fig.19 is a diagram showing a distance measuring device according to a third embodiment. DETAILED DESCRIPTION

[0043] The embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. In this specification and the accompanying drawings, components having substantially the same functional configuration may be represented by the same reference numerals and redundant descriptions thereof may be omitted. In the present disclosure, in the description of the arrangement of components, for a substrate, a direction away from the substrate may be referred to as an upward direction. For example, a film formed to contact the lower surface of a substrate may be referred to as a film formed on the lower surface of the substrate.

[0044] (First embodiment)

[0045] First, a first embodiment will be described. The first embodiment relates to a surface emitting laser module. Figure 1 is a top view showing the surface emitting laser module according to the first embodiment. Figure 2 and Figure 3 is a sectional view showing a surface emitting laser module according to a first embodiment. Figure 2 Corresponding to along Figure 1 A cross-sectional view taken along line II. Figure 3 Corresponding to along Figure 1 A cross-sectional view taken along line II-II. Figure 4 Shown in an enlarged manner Figure 2 Cross-sectional view of a portion of. Figure 5 It is shown in an enlarged manner Figure 3 Cross-sectional view of a portion of. Figure 6 is a bottom view showing a vertical cavity surface emitting laser (VCSEL) chip according to the first embodiment. Figure 7 is a top view showing a VCSEL chip according to the first embodiment. Figure 4 The cross section of the VCSEL chip in corresponds to the Figure 6 A cross section taken along line III-III in FIG. Figure 5 The cross section of the VCSEL chip in corresponds to the Figure 6 A cross section taken along line IV-IV in FIG. Figure 8 is a bottom view showing a microlens array (MLA) according to the first embodiment. Fig. 9 is a cross-sectional view showing the MLA according to the first embodiment.

[0046] like Figures 1 to 5 As shown, the surface emitting laser module 100 according to the first embodiment includes a base substrate 120, a VCSEL chip 140 mounted on the base substrate 120 and including a VCSEL element, and an MLA 160 including a microlens 162 that receives light emitted from the VCSEL element. The VCSEL element is an example of a surface emitting laser element. The VCSEL chip 140 is an example of a surface emitting laser substrate. The microlens 162 is an example of an optical element. The MLA 160 is an example of an optical member. That is, the VCSEL chip 140 is an embodiment of a surface emitting laser substrate.

[0047] In the following description, unless otherwise specified, the direction in which the VCSEL chip 140 is located relative to the base substrate 120 is referred to as upward, and the direction in which the base substrate 120 is located relative to the VCSEL chip 140 is referred to as downward. However, the surface emitting laser module 100 can be used upside down and can be placed at any angle. In addition, the top view refers to the observation of the target object from the direction normal to the upper surface 141b of the VCSEL chip 140. The plane shape refers to the shape of the target object observed from the direction normal to the face 141b of the VCSEL chip 140.

[0048] In each figure, the direction normal to the surface 141b of the VCSEL chip 140 is defined as the Z direction. In the top view, the direction parallel to one side of the surface 141b of the VCSEL chip 140 is defined as the X direction. The direction perpendicular to the X direction and the Z direction is defined as the Y direction.

[0049] <Structure of VCSEL chip 140>

[0050] Here, the structure of the VCSEL chip 140 will be described. In the description of the structure of the VCSEL chip 140 and the method for forming the VCSEL chip 140 described later, the base substrate 120 is defined as the upper side with respect to the direction in which the VCSEL chip 140 is located ( Figures 2 to 5 the -Z direction in).

[0051] As Figure 6 shown, the planar shape of the VCSEL chip 140 is, for example, a quadrilateral, and a light-emitting element unit 158 having a quadrilateral planar shape is substantially disposed at the center of the surface 141a facing the base substrate 120. The surface 141a is an example of the first surface. The surface 141b is an example of the second surface. In the light-emitting element unit 158, a plurality of VCSEL elements 159 are arranged in an array. For example, a total of 36 VCSEL elements 159 are arranged in a 6×6 grid along the X direction and the Y direction. Each of the VCSEL elements 159 is monolithically fabricated on a substrate 141 such as an n-GaAs substrate, and all the VCSEL elements 159 have the same film structure. Each of the VCSEL elements 159 is, for example, a surface-emitting laser having an oscillation wavelength of 940 nm.

[0052] The first electrodes 157 are provided at the four corners of the surface 141a outside the light-emitting element unit 158. A total of 36 second electrodes 155 are provided on the surface 141a, and 9 second electrodes 155 are arranged on each side of the light-emitting element unit 158. The four first electrodes 157 are commonly connected to the n-side electrodes of the 36 VCSEL elements 159. Each of the 36 second electrodes 155 is individually connected to the p-side electrode of the corresponding one of the 36 VCSEL elements 159 through an interconnect 155a. The four corners of the surface 141a refer to the vicinity of the corners of the surface 141a, and the first electrodes 157 do not necessarily need to contact the edge of the surface 141a.

[0053] As Figure 7 shown, a fixing pattern 181 is formed as an adhesion fixing area at the four corners of the surface 141b of the VCSEL chip 140 facing the MLA 160. For example, the fixing pattern 181 has a pattern of a stacked film in which titanium (Ti), platinum (Pt), and gold (Au) are stacked in this order from the surface 141b. The adhesive fixing area is an example of a bonding area.

[0054] For example, the VCSEL element 159 includes a contact layer 142, a semiconductor multilayer reflector 143, a spacer layer 144, an active layer 145, a spacer layer 146, a semiconductor multilayer reflector 147, a selective oxidation layer 151, and a contact layer 148 on a substrate 141 such as an n-GaAs substrate. The selective oxidation layer 151 includes an oxidized region 151a and a non-oxidized region 151b.

[0055] The contact layer 142 is formed on the substrate 141. The contact layer 142 is, for example, an n-GaAs layer.

[0056] The semiconductor multilayer reflector 143 is formed on the contact layer 142. The semiconductor multilayer reflector 143 includes, for example, n-Al 0.9 Ga 0.1 The low refractive index layer made of As and nA l0.2 Ga 0.8 For example, the semiconductor multilayer reflector 143 includes 30 pairs of low refractive index layers and high refractive index layers.

[0057] Between the refractive index layers of the semiconductor multilayer reflector 143, a composition gradient layer having a thickness of, for example, 20 nm is provided, in which the composition gradually changes from one composition to another composition to reduce the resistance. In the case where the oscillation wavelength is represented as λ, the film thickness of each refractive index layer including 1 / 2 of the adjacent composition gradient layer is constructed to have an optical thickness of λ / 4. It should be noted that in the case of an optical thickness of λ / 4, the actual thickness D of the layer is λ / 4n (where n represents the refractive index of the medium of the layer).

[0058] The spacer layer 144 is formed on the semiconductor multilayer reflector 143. The spacer layer 144 is, for example, a non-doped AlGaInP layer.

[0059] The active layer 145 is formed on the spacer layer 144. The active layer 145 is an active layer having a triple quantum well structure, for example, having three quantum well layers and four barrier layers. For example, the quantum well layer is an InGaAs layer, and the barrier layer is an AlGaAs layer.

[0060] The spacer layer 146 is formed on the active layer 145. The spacer layer 146 is, for example, a non-doped AlGaInP layer.

[0061] The portion including the spacer layer 144, the active layer 145 and the spacer layer 146 is also referred to as a resonator structure (resonator region), and is constructed to have an optical thickness of 1 wavelength (λ), including 1 / 2 adjacent composition gradient layers. The active layer 145 is disposed at the center of the resonator structure, which is the position corresponding to the antinode in the standing wave distribution of the electric field, so that a high probability of stimulated emission can be obtained.

[0062] The semiconductor multilayer reflector 147 is formed on the spacer layer 146. For example, the semiconductor multilayer reflector 147 includes a p-Al 0.9 Ga 0.1 The low refractive index layer made of As and the p-Al 0.2 Ga 0.8 For example, the semiconductor multilayer reflector 147 includes 20 pairs of low refractive index layers and high refractive index layers.

[0063] Between the refractive index layers of the semiconductor multilayer reflector 147, a composition gradient layer having a thickness of, for example, 20 nm is provided, in which the composition gradually changes from one composition to another composition to reduce the resistance. Where the oscillation wavelength is expressed as λ, the film thickness of each refractive index layer including 1 / 2 of the adjacent composition gradient layer is constructed to have an optical thickness of λ / 4.

[0064] In the semiconductor multilayer reflector 147, for example, a selective oxidation layer 151 made of p-AlAs with a thickness of 30 nm is inserted. The insertion position of the selective oxidation layer 151 can be, for example, within the second pair of the high refractive index layer and the low refractive index layer counted from the spacer layer 146. It should be noted that the selective oxidation layer 151 may include layers such as a composition gradient layer and an intermediate layer located above and below the selective oxidation layer 151, and here, the layers actually oxidized are collectively referred to as the selective oxidation layer.

[0065] The contact layer 148 is formed on the semiconductor multilayer reflector 147. The contact layer 148 is, for example, a p-GaAs layer.

[0066] A mesa 150a corresponding to the VCSEL element 159 is formed in the light emitting element unit 158 ​​by removing a portion of the contact layer 148, the semiconductor multilayer reflector 147, the spacer layer 146, and the active layer 145 through etching. In addition, a mesa 150b is formed at a position corresponding to the second electrode 155 at the outer side of the light emitting element unit 158. The spacer layer 144 and the semiconductor multilayer reflector 143 are separated between adjacent mesas 150a, and a groove 152 reaching the contact layer 142 is formed.

[0067] An insulating layer 153 is formed to cover the mesas 150a and 150b. For example, SiN, SiON, SiO 2 etc. is used as a material of the insulating layer 153. In the insulating layer 153, an opening portion 154 exposing a portion of the contact layer 148 of each mesa 150a is formed. The opening portion 154 is formed at a position overlapping with the unoxidized region 151b in a top view.

[0068] The p-side electrode 155b, which is electrically connected to the contact layer 148 through the opening portion 154, is formed on the insulating layer 153 independently for each mesa 150a. Each of the p-side electrodes 155b is individually connected to a corresponding one of the second electrodes 155 via the interconnect 155a. For example, the p-side electrode 155b, the interconnect 155a, and the second electrode 155 are configured as a stacked film in which Ti, Pt, and Au are stacked in sequence from the side of the insulating layer 153.

[0069] For the mesa 150b, no opening portion is formed in the insulating layer 153, and the contact layer 148 in the mesa 150b is electrically insulated from the second electrode 155. Therefore, no current flows in the mesa 150b.

[0070] The opening portions 156 are formed at four corners of the insulating layer 153 outside the light-emitting element unit 158 to expose a part of the contact layer 142. The first electrode 157 is formed to be electrically connected to the contact layer 142 through the opening portions 156. The first electrode 157 also serves as the n-side electrode of each VCSEL chip 140. For example, the first electrode 157 has a stacked film in which a gold germanium alloy (AuGe), nickel (Ni), and gold (Au) are stacked in sequence from the side of the contact layer 142.

[0071] On the surface 121a of the base substrate 120 facing the surface 141a, the third electrode 122 bonded to the first electrode 157 and the fourth electrode 123 bonded to the second electrode 155 are formed on the substrate 121. The surface 121a is an example of the third surface. For example, the number of the third electrodes 122 is 4, and the number of the fourth electrodes 123 is 36. The VCSEL chip 140 is flip-chip mounted on the base substrate 120. The third electrode 122 and the fourth electrode 123 are, for example, Au coating films with a thickness of 2 μm.

[0072] <Structure of the MLA 160>

[0073] Hereinafter, the MLA 160 will be described.

[0074] The MLA 160 has a transparent substrate 161 made of, for example, quartz glass. The lens region 166 is provided in a substantially central portion of the surface of the MLA 160 facing the VCSEL chip 140. For example, in the lens region 166, a total of 36 microlenses 162 are arranged in an array at positions corresponding to the respective VCSEL elements 159. Each microlens 162 is designed to perform a desired beam shaping on the radiation pattern of the VCSEL element 159. For example, the lens diameter is 45 μm and the focal length is 70 μm.

[0075] The antireflection film 168 is formed on both sides of the MLA 160. The antireflection film 168 is, for example, one in which HfO 2and SiO 2 The stacked films are stacked in order from the transparent substrate 161 side, and are designed to have a transmittance of 99% or more for light in a predetermined wavelength region including 940 nm, that is, the oscillation wavelength of the VCSEL element 159 .

[0076] The leg portions 163 for defining the distance from the VCSEL chip 140 are formed to extend from the transparent substrate 161 at four corners of the face of the MLA 160 facing the VCSEL chip 140. A fixing pattern 164 is formed as an adhesive fixing area on the bottom surface of the leg portion 163. For example, the fixing pattern 164 has a pattern of stacked films in which Ti, Pt, and Au are stacked in order by vapor deposition from one side of the leg portion 163.

[0077] Each of the fixing patterns 164 is not required to be formed on the entire bottom surface of the leg portion 163 as long as the fixing pattern 164 is formed at a position facing the corresponding fixing pattern 181. The planar shape of the fixing pattern 164 is preferably equal to the planar shape of the fixing pattern 181.

[0078] like Figure 4 As shown in FIGS. 1 and 1, the fixing pattern 164 and the fixing pattern 181 are bonded to each other by an adhesive 182 such as low temperature solder. The adhesive 182 is an example of a bonding member.

[0079] In the surface emitting laser module 100 configured as described above, the VCSEL element 159 emits light from the face 141 b of the VCSEL chip 140 , and the emitted light enters the microlens 162 to form parallel light.

[0080] <Method for Forming VCSEL Chip 140>

[0081] Hereinafter, a method for forming the VCSEL chip 140 will be described. FIG. 10A to FIG. 10G 1 is a cross-sectional view showing a method of manufacturing the VCSEL chip 140 . FIG. 10A to FIG. 10G Shown along Figure 6 Changes in the cross section taken along line III-III. FIG. 11A to FIG. 11G Shown along Figure 6 Changes in the cross section taken along line IV-IV.

[0082] First, if Fig. 10AAs shown, the contact layer 142, the semiconductor multilayer reflector 143, the spacer layer 144, the active layer 145, the spacer layer 146, the semiconductor multilayer reflector 147 and the contact layer 148 are sequentially grown on the substrate 141. For example, a selective oxidation layer 151 (not shown) made of p-AlAs is included in the semiconductor multilayer reflector 147. The semiconductor stacked structure including the contact layer 142, the semiconductor multilayer reflector 143, the spacer layer 144, the active layer 145, the spacer layer 146, the semiconductor multilayer reflector 147 and the contact layer 148 can be prepared, for example, by crystal growth according to a metal organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy (MBE) method. Here, an example using the MOCVD method will be described. For example, trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMI), etc. are used as group III materials, and phosphine (PH 3 ) and arsine (AsH 3 ) is used as a Group V material. For example, carbon tetrabromide (CBr 4 ) is used as a p-type dopant material, hydrogen selenide (H 2 For example, the substrate 141 is an n-GaAs substrate, and its surface is a mirror-polished surface.

[0083] Next, a resist pattern (not shown) is formed on the contact layer 142 according to the desired planar shape of the mesas 150a and 150b by using photolithography. Then, for example, by using Cl 2 The portion of the semiconductor stack structure not covered by the resist pattern is etched by an electron cyclotron resonance (ECR) etching method using a gas. Fig. 10B and Fig.11A As shown, mesas 150a and 150b are formed. At this time, the mesas 150a and 150b are formed so as to expose at least the selective oxidation layer 151 (not shown). After etching, the resist pattern is removed. The bottom surface of the etching may be, for example, the upper surface of the spacer layer 144.

[0084] Next, if Fig. 10C and Fig. 11B As shown, in steam, heat treatment (oxidation treatment) is applied to the semiconductor stacked structure as an oxidation target, in which the mesas 150a and 150b are formed. As a result, Al (aluminum) in the selective oxidation layer 151 is selectively oxidized from the periphery of the mesas 150a and 150b. Then, the unoxidized area 151b that is not oxidized and surrounded by the oxidized area 151a of Al is left in the center of each of the mesas 150a and 150b. As a result, an oxide confinement structure that limits the driving current path of the light-emitting unit only to the central part of the mesas 150a is formed. The non-oxidized area 151b is a current passing area (current injection area).

[0085] Next, if Fig. 10D and Fig. 11C As shown, using photolithography technology, a resist pattern (not shown) is formed on the contact layer 142 and the spacer layer 144 according to the planar shape of the groove 152. The resist pattern is formed so as to expose the area where the first electrode 157 will be formed. Then, by using, for example, Cl 2 The gas ECR etching method etches the portion of the semiconductor stacked structure not covered by the resist pattern, thereby forming a groove 152 reaching the contact layer 142. At this time, the contact layer 142 is exposed in the region where the first electrode 157 is to be formed. After etching, the resist pattern is removed.

[0086] Next, if Fig.10E and Fig.11D As shown, for example, a plasma CVD method is used to form a light-transmitting insulating layer 153 so as to continuously cover the upper and side surfaces of the mesas 150a and 150b, the upper surface and inner wall of the spacer 144 (the bottom surface and side surfaces of the groove 152). Examples of the material of the insulating layer 153 include SiN, SiON, SiO 2 wait.

[0087] Next, if Fig.10F As shown, the insulating layer 153 formed on a portion of the upper surface of the mesa 150a (excluding the peripheral portion of the upper surface of the contact layer 148) is removed by photolithography to form a window, thereby forming an opening portion 154 (contact region).

[0088] Next, if Figure 10G and Fig.11E As shown, the p-side electrode 155b, the interconnection 155a, and the second electrode 155 are formed by forming a resist pattern by photolithography, forming a metal film, and performing lift-off. When forming the metal film, for example, Ti, Pt, and Au are sequentially stacked on the insulating layer 153 and the contact layer 148 exposed by the opening portion 154 by vapor deposition.

[0089] Next, if Fig.11F As shown, by using a photolithography technique, a portion of the insulating layer 153 is removed to form a window in each region where the first electrode 157 is to be formed, thereby forming an opening portion 156 (contact region).

[0090] Next, if Fig.11G As shown, a resist pattern is formed by photolithography, a metal film is formed, and lift-off is performed to form a first electrode 157 serving as an n-side electrode. When forming the metal film, for example, AuGe, Ni, and Au are sequentially stacked on the contact layer 142 exposed through the opening portion 156 by vapor deposition.

[0091] As described above, the VCSEL chip 140 may be formed.

[0092] <Method for Manufacturing Surface Emitting Laser Module 100>

[0093] Next, a method for manufacturing the surface emitting laser module 100 using the base substrate 120 , the VCSEL chip 140 , and the MLA 160 will be described.

[0094] In this method, first, the VCSEL chip 140 is flip-chip mounted on the base substrate 120. As described above, the third electrode 122 bonded to the first electrode 157 and the fourth electrode 123 bonded to the second electrode 155 are formed on the base substrate 120. The VCSEL chip 140 is placed above the base substrate 120 so that the first electrode 157 and the third electrode 122 face each other and the solder is sandwiched between them, and the second electrode 155 and the fourth electrode 123 face each other and the solder is sandwiched between them, and the solder is melted and solidified by heating and cooling. As described above, flip-chip bonding can be performed. Examples of available solders include lead-free solder balls.

[0095] Next, the MLA 160 is bonded to the VCSEL chip 140, for example, by a self-alignment method. That is, the relative positions of the VCSEL chip 140 and the MLA 160 are adjusted so that the fixed pattern 164 and the fixed pattern 181 are almost overlapped in the top view, and a low-temperature solder is provided between the fixed pattern 164 and the fixed pattern 181 as an adhesive 182. For example, examples of available low-temperature solders include solders having a melting point of about 140 degrees Celsius. Next, the MLA 160 bonded to the VCSEL chip 140 is heated in a nitrogen atmosphere to melt the low-temperature solder. The melted low-temperature solder diffuses between the fixed pattern 181 of the VCSEL chip 140 and the fixed pattern 164 of the MLA 160. At this time, self-alignment occurs due to the restoring force of the melted low-temperature solder, and the MLA 160 can be aligned with the VCSEL chip 140 with high precision. In addition, by applying the same amount of low-temperature solder to the combination of the fixed pattern 181 and the fixed pattern 164 at four positions, the accuracy in the height direction can be ensured. For example, the amount of low-temperature solder is adjusted so that the distance between the VCSEL chip 140 and the MLA 160 is 100 μm. Thereafter, through the cooling process, the bonding of the MLA 160 is completed. For example, a bonding method according to a self-alignment method is described in Japanese Unexamined Patent Application Publication No. 2016-40822.

[0096] Here, the effect of the present embodiment will be described in comparison with a reference example. Fig.12 is a cross-sectional view showing a surface emitting laser module according to a reference example. Fig.13 is a top view showing a VCSEL chip of a reference example.

[0097] The surface emitting laser module 900 according to the reference example includes a base substrate 920 , a VCSEL chip 940 mounted on the base substrate 920 and including a VCSEL element, and an MLA 160 .

[0098] The planar shape of the VCSEL chip 940 is a quadrilateral, and the light emitting element unit 958 whose planar shape is a quadrilateral is provided at a substantially central portion of the face 941b facing the MLA 960. In the light emitting element unit 958, a total of 36 mesas 950a corresponding to the VCSEL element are arranged in a 6×6 grid in the X direction and the Y direction. The fixing pattern 981 is formed as an adhesive fixing area at the four corners of the face 941b at the outside of the light emitting element unit 958. The non-metallic area 983 is provided around the fixing pattern 981.

[0099] On the face 941b, a total of 36 second electrodes 955 are arranged such that 9 second electrodes 955 are arranged along each side of the light emitting element unit 958. Each of the 36 second electrodes 955 is individually connected to the p-side electrode of a corresponding one of the VCSEL elements via an interconnect 955a. The n-side electrodes of the 36 VCSEL elements are formed on the face 941a at the side opposite to the face 941b of the VCSEL chip 940, and are commonly connected to an electrode 922 formed on a substrate 921 of a base substrate 920. In addition, each of the 36 second electrodes 955 is individually connected to a corresponding one of the 36 electrodes 923 formed on a substrate 921 of a base substrate 920 via a bonding wire 959. The second electrode 955 is arranged outside a quadrilateral constituted by four fixing patterns 981 in a top view so as to ensure a space for the bonding wire 959 and a limitation on the area due to the non-metal region 983.

[0100] When the planar shape and area size of the light emitting element unit 158 ​​are the same as those of the light emitting element unit 958 , the area size of the VCSEL chip 140 according to the first embodiment is smaller than that of the VCSEL chip 940 according to the reference example.

[0101] For example, in the first embodiment, the face 141a provided with the second electrode 155 is different from the face 141b provided with the fixing pattern 181. Therefore, the fixing pattern 181 may overlap with at least one of the first electrode 157 and the second electrode 155 in a top view as long as the fixing pattern 181 is outside the path of light emitted from the VCSEL element 159.

[0102] In the reference example, the second electrode 955 and the fixed pattern 981 are arranged on the same surface 941b. For this reason, a non-metallic region 983 is arranged around the fixed pattern 981 to ensure insulation performance. For example, in the case where the diameter of the fixed pattern 981 is 400 μm, the outer diameter of the non-metallic region 983 is 800 μm. Therefore, the VCSEL chip 940 requires a large area to arrange the fixed pattern 981.

[0103] In addition, in order to avoid contact between the bonding wire 959 and the MLA 160, the second electrode 955 is disposed outside the MLA 160 in the top view. For example, in the case where the distance from the base substrate 920 to the vertex of the bonding wire 959 is 120 μm and the distance from the base substrate 920 to the lower end of the microlens 162 is 100 μm, the bonding wire 959 contacts the MLA 160 unless the second electrode 955 is disposed outside the MLA 160 in the top view. Therefore, the VCSEL chip 940 requires a large area to dispose the second electrode 955.

[0104] In the case where the distance from the base substrate 920 to the lower end of the microlens 162 is greater than 120 μm, contact can be avoided, but in this case, the focal length of the microlens 162 needs to be increased. In order to increase the focal length, the lens diameter must be increased. The increase in the lens diameter leads to an increase in the spacing between the microlens 162 and the VCSEL element. Therefore, also in this case, the size of the VCSEL chip 940 increases.

[0105] In contrast, the first embodiment has no such limitation. Therefore, according to the first embodiment, the size of the VCSEL chip 140 can be reduced. The reduction in size of the VCSEL chip 140 leads to an increase in the number of VCSEL chips 140 that can be cut from a wafer of any given size, which results in the effect of reducing the cost of the VCSEL chip 140.

[0106] The planar shape of the light emitting element unit 158 ​​does not need to be a quadrilateral, but may be as follows: Fig.14 In this case, on the face 141 b facing the MLA 160 , the fixed pattern 181 may be disposed at a position that does not overlap with the first electrode 157 or the second electrode 155 in the top view.

[0107] Furthermore, the arrangement of the VCSEL elements 159 in the light emitting element unit 158 ​​is not necessarily required to be in an array. For example, the VCSEL elements 159 may be arranged in a honeycomb arrangement.

[0108] (Second embodiment)

[0109] Next, a second embodiment will be described. The second embodiment relates to a surface emitting laser module. Fig.15is a top view showing a surface emitting laser module according to a second embodiment. Fig.16 is a sectional view showing a surface emitting laser module according to a second embodiment. Fig.16 Corresponding to the Fig.15 A cross-sectional view taken along line II. Fig.17 Shown in an enlarged manner Fig.16 Cross-sectional view of a portion of.

[0110] like Figures 15 to 17 As shown, the surface emitting laser module 200 according to the second embodiment includes a base substrate 220, a VCSEL chip 140 mounted on the base substrate 220 and including a VCSEL element, and an MLA 260 including a microlens 262 that receives light emitted from the VCSEL element. The VCSEL element is an example of a surface emitting laser element. The VCSEL chip 140 is an example of a surface emitting laser substrate. The microlens 262 is an example of an optical element. The MLA 260 is an example of an optical member.

[0111] In the present embodiment, the fixed pattern 181 is not formed on the face 141 b of the VCSEL chip 140 .

[0112] On the face 221a of the base substrate 220 facing the face 141a, the third electrode 122 bonded to the first electrode 157 and the fourth electrode 123 bonded to the second electrode 155 are formed on the substrate 221. For example, the number of the third electrodes 122 is 4, and the number of the fourth electrodes 123 is 36. The VCSEL chip 140 is flip-chip mounted on the base substrate 120. In the top view, the fixing pattern 281 is formed as an adhesive fixing area at the four corners of the substrate 221 at the outside of the VCSEL chip 140. The fixing pattern 281 has a pattern in which stacked films of Ti, Pt, and Au are stacked in order from the substrate 221 side.

[0113] The MLA 260 has a transparent substrate 261 made of, for example, quartz glass. The transparent substrate 261 is formed to be wider than the VCSEL chip 140 in the top view, and is wider than the transparent substrate 161 in the first embodiment. The lens area is set in a substantially central portion of the face of the MLA 260 facing the VCSEL chip 140. For example, a total of 36 microlenses 262 are arranged in an array at positions corresponding to the respective VCSEL elements 159 in the lens area. Each microlens 262 is designed to perform desired beam shaping on the radiation pattern of the VCSEL element 159. For example, the lens diameter is 45 μm and the focal length is 70 μm. Anti-reflection films are formed on both sides of the MLA 260.

[0114] Leg portions 163 for defining a distance from the base substrate 220 are formed to extend from the transparent substrate 261 at four corners of the MLA 260 facing the VCSEL chip 140. On the bottom surface of the leg portion 163, a fixing pattern 164 is formed as an adhesive fixing area.

[0115] The fixing pattern 164 and the fixing pattern 281 are bonded to each other by an adhesive 282 such as low temperature solder. The MLA 260 is bonded to the base substrate 220 by, for example, a self-alignment method. The adhesive 282 is an example of a bonding member.

[0116] In the first embodiment, the VCSEL chip 140 includes an area for the fixing pattern 181 regardless of the sizes of the first and second electrodes 157 and 155. Therefore, the size of the VCSEL chip 140 may be affected by the size of the fixing pattern 181 when the first and second electrodes 157 and 155 are relatively small.

[0117] In the second embodiment, the fixing pattern 281 is disposed on the base substrate 220. Therefore, the VCSEL chip 140 does not require an area for the fixing pattern. Therefore, the size of the VCSEL chip 140 is not affected by the size of the fixing pattern 181, and when the first electrode 157 and the second electrode 155 are small, the size of the VCSEL chip 140 can be reduced accordingly.

[0118] It should be noted that the fixing pattern 164 and the fixing pattern 281 need not be bonded by a single adhesive 282, e.g. Fig.18 As shown, a spacer 385 may be provided between the fixing pattern 164 and the fixing pattern 281. In this modification, the spacer 385 is fixed to the fixing pattern 281 by an adhesive 383, and the fixing pattern 164 is fixed to the spacer 385 by an adhesive 382. The combination of the adhesive 382, ​​the spacer 385, and the adhesive 383 is an example of a bonding member.

[0119] In order for the MLA 260 to sufficiently receive light emitted from the VCSEL element 159, it is desirable that the distance between the VCSEL chip 140 and the MLA 260 varies by ±3 μm or less. For example, in a case where the height of the VCSEL chip 140 is 250 μm and the distance between the face 141 b of the VCSEL chip 140 and the lower end of the microlens 262 is attempted to be set to 100 μm, the distance from the upper surface of the base substrate 220 to the lower end of the microlens 262 is 350 μm. For such a long distance, i.e., 350 μm, it is difficult to reduce the variation to ±3 μm or less using only the surface tension of the adhesive 282 such as a single-chip solder or the like.

[0120] In this modification, a spacer 385 is provided. Therefore, the amount of adhesives 382 and 383 is smaller, and the variation in distance is reduced by the surface tension of the adhesives 382 and 383, and bonding can be performed with high precision. For example, low temperature solder can be used as the adhesives 382 and 383.

[0121] Examples of the material of the spacer 385 include silicon (Si) and quartz. Si has the advantages of low material cost and easy processing. Since quartz has a thermal expansion coefficient close to that of the substrate 141 of the VCSEL chip 140, quartz has an advantage in that the amount of change in the distance between the VCSEL chip 140 and the MLA 260 can be reduced even when the VCSEL chip 140 generates heat during operation.

[0122] The oscillation wavelength of the VCSEL element is not limited to the 940 nm band, and may be, for example, the 980 nm band, the 1.3 μm band, or the 1.5 μm band. The material constituting the VCSEL element is not limited, and AlGaInAs or GaInPAs may be used for the VCSEL element. In addition, the composition of each compound semiconductor layer is not particularly limited.

[0123] In addition, the material of the MLA is not limited to quartz glass, for example, borosilicate glass can also be used. The radius of curvature of the microlens can be designed according to the refractive index of the material. The microlens can be arranged on one side of the transparent substrate opposite to the VCSEL chip.

[0124] The MLA bonding method is not limited to the self-alignment method. For example, bonding can be performed by a passive alignment method or an active alignment method. In the passive alignment method, for example, the MLA can be aligned using alignment marks provided on the VCSEL chip or the base substrate and alignment marks provided on the MLA. For example, in the active alignment method, the MLA can be adjusted to an optically appropriate position by moving the MLA while the VCSEL chip is emitting light. When these bonding methods are adopted, for example, an ultraviolet (UV) curable resin or a thermosetting resin can be used as an adhesive. When bonding is performed according to the self-alignment method, a fixed pattern may not be used.

[0125] The VCSEL chip 140 is an individually driven VCSEL chip capable of individually driving each VCSEL element 159. However, the VCSEL chip used in the present disclosure may be a commonly driven VCSEL chip that commonly drives the VCSEL elements in the chip. In the commonly driven VCSEL chip, the number of second electrodes may be reduced. A surface emitting laser module including a commonly driven VCSEL chip may also achieve the effect of reducing the size of the VCSEL chip.

[0126] Alternatively, an electrode on the mesa corresponding to each VCSEL element, such as a p-side electrode, can be directly bonded to an electrode on the base substrate as a second electrode. In this case, in the top view, there is no need to provide a second electrode outside the light emitting element unit of the VCSEL chip.

[0127] (Third Embodiment)

[0128] Next, a third embodiment will be described. The third embodiment relates to a distance measuring device. The distance measuring device is an example of an optical device. Fig.19 is a diagram showing a distance measuring device according to a third embodiment.

[0129] The distance measuring device 400 according to the third embodiment includes a light projecting unit 410 , a light receiving unit 420 , a time measuring circuit 430 , and a control circuit 440 .

[0130] The light projection unit 410 includes, for example, a light source 411, a light source driving circuit 412, an optical scanner 413, an optical scanner driving circuit 414, a scanning angle monitor 415, and a projection lens 416. The light source 411 includes a VCSEL module according to the first or second embodiment. The light source driving circuit 412 drives the light source 411 based on a driving signal output from the control circuit 440. The optical scanner 413 includes a MEMS (micro-electromechanical system) reflector, a polygonal reflector, etc. The optical scanner driving circuit 414 drives the optical scanner 413 based on a driving signal output from the control circuit 440. The VCSEL module of the light source 411 has a plurality of light-emitting sub-regions. Each light-emitting sub-region includes one or more VCSEL elements, and the VCSEL elements in each light-emitting sub-region are electrically connected in parallel. The light-emitting sub-regions are arranged one-dimensionally in the scanning direction (sub-scanning direction) of the optical scanner 413 and can be driven individually. The VCSEL module of the light source 411 is driven by the light source driving circuit 412 with a pulse current of, for example, nanoseconds. The laser light emitted from the VCSEL element is transformed into a desired beam profile by a projection lens 416 or the like as necessary, after which the light emission direction is determined by the optical scanner 413, and the light is emitted to the outside of the distance measuring device 400. The scanning angle of the optical scanner 413 is measured by a scanning angle monitor 415, and the result is output to the control circuit 440. The optical scanner 413 and the projection lens 416 are examples of a second optical element.

[0131] The laser light emitted to the outside of the distance measuring device 400 is reflected by the target object, returns to the distance measuring device 400 , and reaches the light receiving unit 420 .

[0132] The light receiving unit 420 includes, for example, a light receiving element 421, a light receiving lens 422, and a band pass filter 423. The light receiving element 421 includes an APD (avalanche photodiode) element of silicon. The light receiving lens 422 converges the light reaching the light receiving unit 420 on the light receiving element 421. The band pass filter 423 includes a dielectric multilayer and is designed to transmit only light within the range of the oscillation wavelength of the light source 411. The band pass filter 423 can improve the signal-to-noise (S / N) ratio of the signal.

[0133] The light reaching the light receiving element 421 is converted into an electric signal by the light receiving element 421 , and is input to the time measurement circuit 430 through the amplifier 431 and the comparator 432 as necessary.

[0134] The time measurement circuit 430 receives the driving signal of the light source 411 output from the control circuit 440 and the signal from the light receiving element 421. The time measurement circuit 430 measures the delay time between the two signals and outputs the result to the control circuit 440.

[0135] The control circuit 440 converts the delay time from the time measurement circuit 430 into the wavelength of light.

[0136] According to the distance measuring device 400, two-dimensional distance information can be obtained by measuring the distance to the target object by sequentially emitting laser light to the spatial area decomposed by the light emitting sub-areas of the VCSEL module and the light scanner 413. The distance measuring device 400 can be used for example in LiDAR (Light Detection and Ranging).

[0137] In addition to the distance measuring device light source, the surface emitting laser module according to the present disclosure can be used as an excitation light source for a solid-state laser. The surface emitting laser module can be used as a light source device such as a projector in combination with an optical element such as a phosphor, which converts the wavelength of the emitted light from the surface emitting laser module. The surface emitting laser module can also be used as a light source device for sensing in combination with an optical element (e.g., a lens, a reflector, or a diffraction grating), which diverges or converges the emitted light from the surface emitting laser module.

[0138] The preferred embodiments and the like have been described in detail above, but the present invention is not limited to the above embodiments and the like, and various modifications and substitutions may be made to the above embodiments and the like without departing from the scope described in the claims.

[0139] Reference numerals list

[0140] 100, 200 Surface Emitting Laser Modules

[0141] 120, 220 base substrate

[0142] 140 VCSEL chips

[0143] 150a, 150b countertop

[0144] 155 Second electrode

[0145] 157 First Electrode

[0146] 158 Light emitting element unit

[0147] 159 VCSEL Components

[0148] 160,260 MLA

[0149] 162 Microlens

[0150] 164, 181, 281 fixed pattern

[0151] 182, 282, 382, ​​383 Adhesives

[0152] 385 Spacer

[0153] 400 Distance measuring device

[0154] 411 Light Source

[0155] Citation list

[0156] Patent Literature

[0157] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2007-142425

[0158] This application is based upon and claims the benefit of priority from Japanese Priority Application No. 2019-016353, filed on January 31, 2019, the entire contents of which are incorporated herein by reference.

Claims

1. A surface emitting laser module, comprising: basal substrate; a surface emitting laser substrate mounted on the base substrate, the surface emitting laser substrate including a surface emitting laser element and having a first face facing the base substrate and a second face facing away from the base substrate; and an optical member facing the second face and including an optical element configured to receive light emitted from the second face of the surface emitting laser element, wherein the surface emitting laser element comprises: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type; a first electrode disposed on the first face and connected to the first semiconductor layer; and a second electrode disposed on the first surface and connected to the second semiconductor layer, wherein the base substrate has a third surface facing the first surface of the surface emitting laser substrate, and comprises: a third electrode disposed on the third face and connected to the first electrode; and a fourth electrode, which is disposed on the third surface and connected to the second electrode, wherein the first electrode and the second electrode are disposed away from a light emitting element unit including an array of a plurality of mesas configured to generate light in the surface emitting laser element, and The second electrode and the current injection region of the mesa are connected by an interconnect.

2. The surface emitting laser module according to claim 1, further comprising a bonding member bonding the optical member to the base substrate and the surface emitting laser substrate, in, The bonding member is provided at a position different from the surface emitting laser element as viewed from a direction perpendicular to the second face of the surface emitting laser substrate.

3. The surface emitting laser module according to claim 2, wherein: A bonding member is provided on an outer side relative to the surface emitting laser element as viewed from a direction perpendicular to the second face of the surface emitting laser substrate.

4. The surface emitting laser module according to claim 2 or 3, wherein: The bonding member bonds an optical member to the second face of the surface emitting laser substrate.

5. The surface emitting laser module according to claim 4, wherein When viewed from a direction perpendicular to the second face of the surface emitting laser substrate, at least a portion of the bonding member is included in a region including the first electrode and the second electrode.

6. The surface emitting laser module according to claim 4 or 5, wherein: When viewed from a direction perpendicular to the second face of the surface emitting laser substrate, at least a portion of the bonding member overlaps with the first electrode or the second electrode, or overlaps with both the first electrode and the second electrode.

7. The surface emitting laser module according to claim 2 or 3, wherein: The coupling member couples the optical member to the third surface of the base substrate.

8. The surface emitting laser module according to claim 7, wherein When viewed from a direction perpendicular to the second face of the surface emitting laser substrate, a first electrode and a second electrode are provided on a side of the surface emitting laser element opposite to the bonding member.

9. The surface emitting laser module according to claim 7 or 8, wherein: The coupling member includes a spacer inserted between the optical member and the base substrate.

10. The surface emitting laser module according to claim 1, wherein The surface emitting laser substrate is flip-chip mounted on the base substrate.

11. The surface emitting laser module according to claim 1 or 2, wherein: The surface emitting laser element includes an active layer between a first semiconductor layer and a second semiconductor layer.

12. An optical device comprising: A surface emitting laser module according to any one of claims 1 to 11; and A second optical element is configured to receive light emitted from the surface emitting laser module.

13. An optical device comprising: A surface emitting laser module according to any one of claims 1 to 11; and A light receiving unit is configured to receive light emitted by the surface emitting laser module and reflected by or passing through a target object.

14. A surface emitting laser substrate having a first surface and a second surface opposite to the first surface, the surface emitting laser substrate comprising: a surface emitting laser element configured to emit light from the second surface, wherein the surface emitting laser element comprises: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type; a first electrode disposed on the first face and connected to the first semiconductor layer; and a second electrode disposed on the first surface and connected to the second semiconductor layer, wherein the first electrode and the second electrode are disposed away from a light emitting element unit including an array of a plurality of mesas configured to generate light in the surface emitting laser element, and The second electrode and the current injection region of the mesa are connected by an interconnect.

15. The surface emitting laser substrate according to claim 14, wherein The surface emitting laser element includes an active layer between a first semiconductor layer and a second semiconductor layer.

16. The surface emitting laser substrate according to claim 14 or 15, further comprising: a bonding region provided on the second face to be bonded with an optical element that receives light emitted from the surface emitting laser element, wherein the bonding region is provided at a position different from that of the surface emitting laser element as viewed from a direction perpendicular to the second face.

17. The surface emitting laser substrate according to claim 16, wherein The bonding region is provided on an outer side relative to the surface emitting laser element as viewed from a direction perpendicular to the second face of the surface emitting laser substrate.

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