Abstract
A method for producing micro-optics on surface-emitting laser diodes. In a wafer-level operation, the micro-optics are preferably positioned directly on the VCSEL's forming, in each instance, a part of a coherent wafer.
Claims
1. A method for producing micro-optics on surface-emitting laser diodes (VCSEL's), the method comprising: in a wafer-level operation, positioning the micro-optics directly on the VCSEL's, forming, in each instance, a part of a coherent wafer.
2. The method as recited in claim 1, further comprising: manufacturing a wafer having a plurality of VCSEL's; applying an unfunctionalized photopolymer to the wafer having the VCSEL's; and imprinting specific optical functions of the micro-optics assigned, in each instance, to one of the VCSEL's of the wafer.
3. The method as recited in claim 2, wherein the photopolymer is bonded or laminated onto the wafer having the VCSEL's.
4. The method as recited in claim 2, wherein the photopolymer is applied in liquid form to the wafer having the VCSEL's, in a spin-on operation or in a screen-printing operation.
5. The method as recited in claim 2, wherein prior to, during, or after the positioning of the micro-optics and, after the application of the photopolymer, the VCSEL's of the wafer are characterized by a laser pulse, the laser pulse being generated by activating the VCSEL's of the wafer.
6. The method as recited in claim 5, wherein the laser pulses leaving wafer are measured by a sensor, and measuring results of the sensor specific to each VCSEL are taken into consideration during the imprinting of the optical functions into the corresponding VCSEL's.
7. The method as recited in claim 5, wherein a duration of the laser pulse, which is used in the characterization of each VCSEL which takes place after the application of the unfunctionalized photopolymer, is selected to be temporally brief in such a manner that exposure of the photopolymer is at least substantially prevented.
8. The method as recited in claim 2, wherein during the imprinting, a transmission hologram is produced in the photopolymer.
9. The method as recited in claim 8, wherein two different exposure wavefronts are used for producing the transmission hologram.
10. The method as recited in claim 9, wherein a first exposure wavefront of the two exposure wavefronts is provided for producing the optical function, and a second exposure wavefront of the two exposure wavefronts is provided to compensate for manufacturing-specific characteristics of the VCSEL, which are ascertained in light of the VCSEL characterization.
11. The method as recited in claim 10, wherein using the first exposure wavefront and/or using the second exposure wavefront, a correction of a peak wavelength generated by the VCSEL is imprinted into the transmission hologram using Bragg equations.
12. The method as recited in claim 9, wherein the two different exposure wavefronts are coherent with respect to each other and/or are generated by a common source of radiation, the common source of radiation being a common spatial light modulator.
13. A wafer, including a plurality of surface-emitting laser diodes having micro-optics, which are positioned directly on an upper side of the wafer and are produced by positioning, in a wafer-level operation, the micro-optics directly on the VCSEL's, forming, in each instance, a part of a coherent wafer.
14. The wafer as recited in claim 13, wherein the micro-optics form transmission holograms.
15. Surface-emitting laser diodes, manufactured from a sectioned wafer, the wafer including a plurality of surface-emitting laser diodes having micro-optics, which are positioned directly on an upper side of the wafer and are produced by positioning, in a wafer-level operation, the micro-optics directly on the VCSEL's, forming, in each instance, a part of a coherent wafer.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Further advantages are derived from the description of the figures. An exemplary embodiment of the present invention is depicted in the figures. The figures and the description include numerous features in combination. One skilled in the art will necessarily consider the features individually, as well, and unite them to form useful, further combinations.
[0025] FIG. 1 shows a schematic representation of a manufacturing device for producing VCSEL's provided with micro-optics in a wafer-level operation, according to an example embodiment of the present invention.
[0026] FIG. 2 shows a schematic cross section of a part of a wafer having VCSEL's, prior to the imprinting of an optical function of the micro-optics, according to an example embodiment of the present invention.
[0027] FIG. 3 shows a further schematic cross section of a part of a wafer having VCSEL's, during the imprinting of the optical function, according to an example embodiment of the present invention.
[0028] FIG. 4 shows a schematic flow chart of a method for producing the micro-optics on the VCSEL's, according to an example embodiment of the present invention.
[0029] FIG. 5 shows a schematic exposure curve of the photopolymer, from which the micro-optics are produced by imprinting, according to an example embodiment of the present invention.
[0030] FIG. 6 shows a schematic linewidth of the VCSEL and an efficiency curve of a transmission hologram, which the micro-optics form, and which is positioned on the VCSEL, according to an example embodiment of the present invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0031] FIG. 1 schematically shows a manufacturing device 32 for producing surface-emitting laser diodes (VCSEL's) 12 provided with micro-optics 10 (see FIG. 2 or 3). Manufacturing device 32 is at least designed to provide VCSEL's 12 in wafer form with optical functions. Manufacturing device 32 is designed to support a wafer 14. The wafer 14 situated in manufacturing device 32 includes a photopolymer 16. Photopolymer 16 covers a side, in particular, an upper side 30 of wafer 14, in the form of a layer. For each of VCSEL's 12 of wafer 14, manufacturing device 32 is designed to imprint a(n) (specific) optical function into photopolymer 16. (Adapted) Micro-optics 10 are produced for each VCSEL 12 of wafer 14 by imprinting the optical functions (cf. FIG. 2 or 3). Finished wafer 14 then includes a plurality of VCSEL's 12, on each of whose upper sides 30 micro-optics 10 are positioned. Micro-optics 10 form, by way of example, transmission holograms; other optical functions also being possible. After completion of micro-optics 10, wafer 14 is sectioned, so that a plurality of individual surface-emitting laser diodes (12, VCSEL) are formed from wafer 14. The VCSEL's 12 having micro-optics 10 are intended, e.g., for use in smart glasses (not shown).
[0032] Manufacturing device 32 includes a prober 34. Prober 34 is designed to contact individual VCSEL's 12 of wafer 14 electrically. Prober 34 is designed to induce VCSEL's 12 to generate laser pulses 18 (see FIG. 5 or 6), in particular, characterizing and/or test laser pulses. Prober 34 is positioned on a lower side 38 of wafer 14. Prober 34 contacts VCSEL 12 from lower side 38 of wafer 14. Manufacturing device 32 includes an exposure device 36. Exposure device 36 forms a source of radiation. Exposure device 36 is situated on a side of wafer 14 opposite to prober 34, in particular, on an upper side 30 of wafer 14. Exposure device 36 takes the form of a spatial light modulator (SLM). Exposure device 36 is provided for imprinting the optical functions of micro-optics 10 into photopolymer 16. Exposure device 36 is designed to expose each VCSEL 12 of wafer 14 individually. Exposure device 36 is designed to emit at least two different exposure wavefronts 22, 24 for irradiating photopolymer 16. Exposure wavefronts 22, 24 may differ in transmission angle, beam divergence, etc. Exposure device 36 is supported above wafer 14 so as to be precisely positionable (not shown). Exposure device 36 includes adjustable optical axes for generating the two exposure wavefronts 22, 24.
[0033] Manufacturing device 32 includes a sensor 20. Sensor 20 takes the form of a device for measuring the directional and divergence characteristics of the laser pulse 18 leaving wafer 14. By way of example, sensor 20 takes the form of a wavefront sensor. Sensor 20 is situated on a side of wafer 14 opposite to prober 34, in particular, on upper side 30 of wafer 14. Sensor 20 is situated on the same side of wafer 14 as exposure device 36. Sensor 20 is provided for measuring wavefronts, in particular, light pulses generated by VCSEL's 12, in particular, after excitation of the VCSEL's 12 by prober 34. Sensor 20 is designed to measure light pulses, in particular, laser pulses 18 generated, in particular, by VCSEL's 12, in particular, after excitation of the VCSEL's 12 by prober 34. Sensor 20 transmits the measuring results to exposure device 36, which controls and/or carries out the irradiation on the basis of the measuring results.
[0034] FIG. 2 schematically shows a cross section of a part of the wafer 14 having VCSEL's 12, prior to the imprinting of the optical functions. Photopolymer 16 is applied to upper side 30 of wafer 14 in the form of a layer. In the example shown, an adhesive layer 48 is situated between photopolymer 16 and VCSEL 12. Adhesive layer 48 has an index of refraction adapted to an index of refraction of VCSEL 12 and/or of photopolymer 16. Each VCSEL 12 includes an upper Bragg reflector (distributed Bragg reflector (DBR)) 40. Each VCSEL 12 includes a lower Bragg reflector 42. The two Bragg reflectors 40, 42 of VCSEL 12 form an optical resonator 44 of VCSEL 12. VCSEL 12 includes electrical vias 46. Electrical vias 46 may be contacted from lower side 38 of wafer 14, e.g., for prober 34. FIG. 3 schematically shows one of the VCSEL's 12 of FIG. 2 during an imprinting operation, in which photopolymer 16 is exposed to the two exposure wavefronts 22, 24.
[0035] FIG. 4 shows a schematic flow chart of a method for producing micro-optics 10 on VCSEL's 12. In the method, in a wafer-level operation, micro-optics 10 are positioned directly on, in each instance, the VCSEL's 12 forming a part of a coherent wafer 14. In at least one method step 50, the wafer 14 having the plurality of VCSEL's 12 is manufactured. For example, wafer 14 may be manufactured in an epitaxial operation. In at least one further method step 52, the photopolymer 16 that is still unfunctionalized is applied to upper side 30 of the wafer 14 having VCSEL's 12. In method step 52, photopolymer 16 is bonded or laminated onto the wafer 14 having VCSEL's 12. Alternatively, in a method step 52′ alternative to method step 52, photopolymer 16 is applied in liquid form to the wafer 14 having VCSEL's 12. In this case, for example, a spin-on operation or a screen-printing operation are available for applying photopolymer 16. In a further method step 54, photopolymer 16 is subsequently bleached, in particular, in a controlled process, with the aid of a wide-band light spectrum, e.g., with the aid of an incoherent incandescent light. In this context, bleaching of photopolymer 16 prior to the exposure with a controlled dose may also be advantageous, in order to reduce the sensitivity of photopolymer 16 and, thus, the risk of imprinting interfering holograms, in particular, during the VCSEL characterization. In contrast to that, bleaching after the imprinting operation is used for setting the imprinted holographic pattern and bringing photopolymer 16 into a stationary state. As an option, the bleaching may advantageously be combined with a method step necessary for the VCSEL production, e.g., with a sintering process after a deposition. As an additional option, the bleaching may advantageously be carried out in a device, which is already present, in order to, e.g., carry out a characterization on the wafer level, using photoluminescence spectroscopy. In at least one further method step 56, VCSEL's 12 of wafer 14 are characterized by a laser pulse 18 prior to the positioning of micro-optics 10 and after the application of photopolymer 16. Exposure device 36, in particular, the SLM, is controlled with the aid of the measuring results of sensor 20. In method step 56, laser pulse 18 is generated via activation of VCSEL's 12 of wafer 14 by the VCSEL's 12 themselves. A duration of laser pulse 18, which is used in the characterization of VCSEL's 12 taking place after the application of photopolymer 16, is selected to be temporally brief in such a manner, that exposure of photopolymer 16 is at least substantially prevented (cf. FIG. 5 and the corresponding explanations, as well). As an option, the characterization step after the exposure of the holograms may also be advantageously combined with a burn-in step by laser diodes, if a suitable contacting area is present.
[0036] In at least one further method step 58, the specific optical functions are imprinted into the regions of the photopolymer 16 each assigned to one of VCSEL's 12. In method step 58, the micro-optics 10 assigned, in each instance, to one of the VCSEL's 12 of wafer 14 are produced by irradiating photopolymer 16 in a controlled manner, with the aid of exposure device 36. During the imprinting, the optical function is generated in photopolymer 16 in the form of a transmission hologram. In this context, in method step 58, the laser pulses 18 leaving wafer 14 are measured by sensor 20, and the measuring results of sensor 20 specific to each VCSEL 12 are taken into consideration during the imprinting of the optical functions into corresponding VCSEL 12. In method step 58, two different exposure wavefronts 22, 24 are used for generating the transmission hologram. The two exposure wavefronts 22, 24 contribute to the generation of the transmission hologram. The two exposure wavefronts 22, 24 are each selected in such a manner, that the optical function to be produced, in each instance, by interference of exposure wavefronts 22, 24, is produced according to the holographic principle. The two exposure wavefronts 22, 24 are generated by exposure device 36. The two different exposure wavefronts 22, 24 are coherent with respect to each other. The two different exposure wavefronts 22, 24 are generated by a common source of radiation 28 of exposure device 36, in particular, by a common spatial light modulator (SLM). A first exposure wavefront 22 of the two exposure wavefronts 22, 24 is designed to produce the intended optical function (cf. FIG. 3, as well). A second exposure wavefront 24 of exposure wavefronts 22, 24 is to compensate for manufacturing-specific characteristics of the specific VCSEL 12, which were ascertained, in particular, in light of the preceding VCSEL characterization of method step 56 (cf. FIG. 3, as well). With the aid of first exposure wavefront 22 and/or with the aid of second exposure wavefront 24, preferably, with the aid of a combination of exposure wavefronts 24, a correction of a peak wavelength 26 generated by VCSEL 12 (cf. FIG. 6, as well) is imprinted into the transmission hologram, in particular, using the Bragg equations.
[0037] FIG. 5 schematically shows an exposure curve 64 of photopolymer 16, in which an exposure efficiency (y axis) is plotted versus an exposure time. The temporally brief laser pulse 18, which is generated by VCSEL's 12 and is used for characterizing VCSEL's 12, starts at time t=0 and ends at time t=t.sub.1. The temporally brief laser pulse 18, which is generated by VCSEL's 12 and is used for characterizing VCSEL's 12, ends before the exposure efficiency curve of photopolymer 16 rises significantly. In this manner, an unintentional (partial) exposure of photopolymer 16 by laser pulse 18 is effectively prevented.
[0038] FIG. 6 schematically shows a linewidth 60 of a VCSEL 12 with peak wavelength 26, as well as an efficiency curve 62 of the transmission hologram plotted versus the wavelength; the transmission hologram being formed by micro-optics 10 and being positioned on VCSEL 12. An overlap 66 of linewidth 60 and efficiency curve 62 may be set by adjusting the imprinted optical function.
