Patent Publication Number: US-2023163107-A1

Title: Optical projection device having a grid structure

Description:
BACKGROUND 
     Micro-LED (light emitting diode) displays combine very small, individually controllable light sources in a single component. New approaches micro-LED displays combine several technology components from the fields of CMOS (complimentary metal-oxide-semiconductor) thin-film technology, III/V semiconductors, LED design (electrical and optical confinement), and LED packaging for light extraction, wavelength conversion and optical isolation between the pixels. This complex task makes it difficult to manufacture cost-effectively under the premise of not compromising on efficiency and imaging quality. 
     More particularly, designing the optical path from each individual light source to the imaging optics in such a way that there is as little crosstalk as possible between the individual pixels is highly challenging for projection applications. Conventional solutions take this design consideration into account only to a limited extent. Furthermore, very complex solutions are sometimes used to separate the individual pixels. 
     Thus, there is a need for an improved micro-LED display device and corresponding method of production. 
     SUMMARY 
     According to an embodiment of an optical projection device, the optical projection device comprises: a plurality of LEDs (light-emitting diodes), the LEDs each comprising a semiconductor mesa laterally spaced apart from one another by a grid structure, wherein each of the semiconductor mesas comprises an n-type material and a p-type material adjoining at least partly the n-type material, wherein the grid structure at least partly laterally surrounds at least the n-type material of each of the semiconductor mesas, wherein the grid structure comprises a conductive material that electrically interconnects the n-type material of the semiconductor mesas, wherein the grid structure is configured to block optical crosstalk between light emitted by the LEDs. 
     According to an embodiment of a method of producing an optical projection device, the method comprises: providing a plurality of LEDs (light-emitting diodes), the LEDs each comprising a semiconductor mesa laterally spaced apart from one another by an open grid, each of the semiconductor mesas comprising an n-type material and a p-type material adjoining the n-type material; and forming a grid structure in the open grid and that at least partly laterally surrounds at least the n-type material of each of the semiconductor mesas, wherein the grid structure comprises a conductive material that electrically interconnects the n-type material of the semiconductor mesas, wherein the grid structure is configured to block optical crosstalk between light emitted by the LEDs. 
     Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts. The features of the various illustrated embodiments can be combined unless they exclude each other. Embodiments are depicted in the drawings and are detailed in the description which follows. 
         FIG.  1 A  illustrates a partial cross-sectional view of an optical projection device and  FIG.  1 B  illustrates a top perspective view of a section of the device. 
         FIG.  1 C  illustrates a top perspective view of another embodiment of the section of the optical projection device illustrated in  FIG.  1 B . 
         FIGS.  2 A through  2 C  correspond to  FIGS.  1 A through  1 C , respectively, but with a driver device attached to the optical projection device. 
         FIGS.  3 A through  3 D  illustrate partial cross-sectional views of an embodiment of a method of producing the optical projection device. 
         FIG.  4    illustrates a partial cross-sectional view of another embodiment of the optical projection device. 
         FIGS.  5 A and  5 B  illustrate partial cross-sectional views of another embodiment of a method of producing the optical projection device. 
         FIGS.  6 A and  6 B  illustrate partial cross-sectional views of another embodiment of a method of producing the optical projection device. 
         FIG.  7    illustrates a partial cross-sectional view of another embodiment of the optical projection device. 
         FIG.  8    illustrates a partial cross-sectional view of another embodiment of the optical projection device. 
         FIG.  9    illustrates a partial cross-sectional view of different embodiments of forming an open grid shown in  FIG.  3 C . 
     
    
    
     DETAILED DESCRIPTION 
     Described herein are embodiments of an optical projection device having a grid structure for optically confining individual light emitting pixels, and corresponding methods of production. The grid structure at least partly laterally surrounds at least n-type material of each light emitting pixel, and electrically interconnects the n-type material of the light emitting pixels. Accordingly, the grid structure blocks optical crosstalk between light emitted by the individual pixels while providing a simplified electrical connection to the pixels. 
     Described next, with reference to the figures, are exemplary embodiments of the optical projection device and corresponding methods of production. 
       FIGS.  1 A and  1 B  illustrate an embodiment of the optical projection device.  FIG.  1 A  illustrates a partial cross-sectional view of the optical projection device and  FIG.  1 B  illustrates a top perspective view of a section of the device. The optical projection device includes LEDs (light-emitting diodes)  100  which function as light emitting pixels. The optical projection device may include tens, hundreds, thousands or even more individually controllable LEDs  100 . 
     Each LED  100  includes a semiconductor mesa  102  laterally spaced apart from one another by a grid structure  104 . Each semiconductor mesa  102  includes an n-type material  106  and a p-type material  108  adjoining at least partly the n-type material  106  to form a light emitting pn junction  110 . The semiconductor mesas  102  may comprise any type of semiconductor capable of emitting light such as Si, SiC, GaN, etc. In one embodiment, the semiconductor mesas  102  comprise a III/V semiconductor and the LEDs  100  emit blue light and have a width (x dimension in  FIG.  1 B ) of 50 microns. In a plan view, the semiconductor mesas  102  may have a rectangular or square shape, e.g., as shown in  FIG.  1 B , or may have other shapes such as round, hexagonal, octagonal, etc. 
     The grid structure  104  at least partly laterally surrounds at least the n-type material of each semiconductor mesa  102 . The grid structure  104  includes a conductive material  114  such as a metal or metal alloy, carbon nano tubes, a superconductor, etc. that electrically interconnects the n-type material  106  of the semiconductor mesas  102 , simplifying the cathode electrical connection to the pixels  100 . The pixels remain individually controllable via respective anode contacts  112  at the opposite side of the device. In addition to simplifying the cathode electrical connection to the individual light emitting pixels  100 , the grid structure  104  is also configured to block optical crosstalk  101  between light emitted by the LEDs  100 . Accordingly, individual pixels are optically separated from each other by the grid structure  104  and the electrical resistance of the N-side of the pixels is reduced by the conductive material  114  of the grid structure  104  which acts as a current distributor. 
     The conductive material  114  may be Ag which provides superior optical isolation. However, other materials that are electrically conductive and optically blocking may be used. For example, the conductive material  114  may comprise Al, Au or other noble metal, rhodium, titanium oxide, etc. 
     According to the embodiment illustrated in  FIGS.  1 A and  1 B , the semiconductor mesas  102  may be coplanar with the upper surface  116  of the grid structure  104  where coplanar means lying in the same plane or in two different planes that are within process variations. For example, coplanar includes a height difference of about 2 microns or less for process variations that result in 2 microns or less in height variation. In this embodiment, the conductive material  114  of the grid structure  104  terminates at the height of the n-type material  106  such that the conductive material  114  acts as both a current spreading grid and as an optical isolation structure. Furthermore, the conductive material  114  of the grid structure  104  may also act as a cavity for the reception of a conversion material, as described in more detail later herein. In each case, the grid structure  104  allows for high pixel (LED) density and easy implementation of multi-color micro displays. 
     The LEDs  100  may be monolithically integrated as part of a semiconductor wafer or (chip) die  118 . In this case, the grid structure  104  may include a grid of intersecting trenches  120  etched into the semiconductor wafer / die  118  such that the grid of intersecting trenches  120  laterally separates the semiconductor mesas  102  at least partly from one another. According to this embodiment, the conductive material  114  of the grid structure  104  fills the grid of intersecting trenches  120 . 
     Separately or in combination, the grid structure  104  may contact an n-type region  122  of the semiconductor wafer / die  118  that is laterally spaced apart from the semiconductor mesas  102 . According to this embodiment, the n-type region  122  is connected to a common cathode electrode  124  of the optical projection device. The conductive material  114  of the grid structure  104  electrically connects the common cathode electrode  124  to the n-type region  106  of a group of the semiconductor mesas  102 . For example, the conductive material  114  of the grid structure  104  may electrically connect the common cathode electrode  124  to the n-type region  106  of each semiconductor mesa  102  included in the optical projection device or to a subset of the semiconductor mesas  102 . In each case, and as described above, an individual anode electrode  112  is connected to the p-type region  108  of each one of the semiconductor mesas  102  to ensure individual pixel control. Accordingly, only a single individual contact  112  to each LED  100  is required and the size of the LEDs  100  may be reduced by about 50% by using the n-type-region  122  as a global / shared contact. 
     The semiconductor wafer / die  118  may include a dielectric material  126  that, together with the grid structure  104 , provides the physical isolation between the LEDs  100 . The grid structure  104  may have the same line width (w) across the entire optical projection device, e.g., as shown in  FIG.  1 C . Such a configuration allows for a homogeneous structure that is advantageous for manufacturing.  FIG.  1 C  also shows that the n-type-region  122  may be subdivided into sub regions  122 ′ having the same lateral dimensions (x, y in  FIG.  1 C ) as the n-type material  106  of each LED  100  surrounded by the grid structure  104 . 
       FIGS.  2 A through  2 C  correspond to  FIGS.  1 A through  1 C , respectively, but with a driver device  200  attached to the optical projection device. The driver device  200  is configured to drive individual ones of the LEDs  100 . Each of the individual anode electrodes  112  of the optical projection device is connected to a corresponding anode electrode  202  of the driver device  200 . The common cathode electrode  124  of the optical projection device is connected to a cathode electrode  204  of the driver device  200 . The side of the driver device  200  facing the optical projection device may include a passivation  206 , for example. In one embodiment, the driver device  200  is a CMOS (complementary metal-oxide-semiconductor) device and the semiconductor mesas  102  that yield the light emitting pixels of the optical projection device comprise III/V semiconductor material. For example, the driver device  200  may be a TFT (thin film transistor) backplane. However, the driver device  200  may be a different type of driver device than a CMOS driver. For example, the driver device  200  may be a passive matrix instead. Still other driver device options are possible. In general, the driver device  200  is any type of device suitable for individually controlling/driving the individual pixels formed by the LEDs  100  of the optical projection device. 
       FIGS.  3 A through  3 D  illustrate partial cross-sectional views of an embodiment of a method of producing the optical projection device. According to this embodiment, the optical projection device is produced from a semiconductor wafer  118 . 
       FIG.  3 A  shows the semiconductor wafer  118  used to produce the optical projection device vertically aligned with the driver device  200 . The LEDs  100  may have already been produced at this point of the production process. The LEDs  100  instead may be produced later in the production process. In either case, the grid structure  104  has yet to be produced at this point. The driver device  200  may be provided as a separate semiconductor wafer, for example. Instead of the driver device  200 , the semiconductor wafer  118  used to produce the optical projection device may be vertically aligned with a carrier such as another semiconductor wafer, a ceramic substrate, etc. 
       FIG.  3 B  shows the semiconductor wafer  118  attached to the driver device  200 . Each of the individual anode electrodes  112  of the optical projection device is connected to a corresponding anode electrode  202  of the driver device  200  and the common cathode electrode  124  of the optical projection device is connected to a cathode electrode  204  of the driver device  200 , e.g., using solder, a Cu-to-Cu connection, glue or other adhesive, etc. 
       FIG.  3 C  shows an open grid  300  formed in the n-type material  106  of the semiconductor wafer  118  to define the semiconductor mesas  102 . In one embodiment, the open grid  300  is formed by etching a grid of intersecting trenches  302  into the n-type material  106  of the semiconductor wafer such that the grid of intersecting trenches  302  laterally separates the semiconductor mesas  102  from one another. Any standard trench etching process may be used. The trench etching may stop, e.g., on a dielectric material  126 . In another example, the trenches  302  may be etched into the dielectric material  126  to improve stability/anchoring structure for the grid structure  104 . In the case of GaN, e.g., this may involve an over-etch to ensure GaN residues are removed. However, the etching may not reach the dielectric material  126  for all LED cells  100  and some residual GaN may remain. 
       FIG.  3 D  shows a conductive material  114  filling the open grid  300  of intersecting trenches  302  to form the grid structure  104 . The conductive material  114  may be deposited and then planarized, for example. The conductive material  114  may comprise a metal or metal alloy, carbon nano tubes, a superconductor, etc. The conductive material  114  of the grid structure  104  electrically interconnects the n-type material  106  of the semiconductor mesas  102  while also blocking optical crosstalk between light emitted by the LEDs  100 , as previously described herein. The conductive material  114  may also act as a conversion layer for changing the color of light emit by the LEDs  100 . 
       FIG.  4    illustrates a partial cross-sectional view of another embodiment of the optical projection device. According to this embodiment, the grid structure  104  contacts a metal region  400  of the semiconductor wafer  118  that is laterally spaced apart from the semiconductor mesas  102 . The metal region  400  is connected to the common cathode electrode  124  of the optical projection device. The metal region  400  may comprise a metal or metal alloy such as Cu, AlCu, AlSiCu, Al, Au, rhodium, titanium oxide, etc. The metal region  400  provides less resistance than the n-type region  122  for current distribution within the area of the LED cells  100 . 
     Also as shown in  FIG.  4   , the grid structure  104  may have a negative taper. For example, the sidewalls  402  of the conductive material  114  of the grid structure  104  have a negative taper such that the conductive material  114  is wider closer to the dielectric material  126  and narrower further from the dielectric material  126 . In one embodiment, the negative taper of the grid structure  104  is in a range of 1 to 15 degrees (α in enlarged view of  FIG.  4   ) relative to a normal projection  406  onto the semiconductor mesas  102 . Any of the grid structure embodiments described herein may include the negative taper feature which is helpful for re-directing light to the emission layer  106  and through the emission surface  404 . 
       FIGS.  5 A and  5 B  illustrate partial cross-sectional views of another embodiment of a method of producing the optical projection device. In  FIGS.  5 A and  5 B , the optical projection device includes a metal region  400  for current distribution within the area of the LED cells  100 . However, the optical projection device instead may include an n-type region  122  for current distribution within the area of the LED cells  100 . 
       FIG.  5 A  shows at least some of the semiconductor mesas  102  recessed below the upper surface  116  of the grid structure  104  to form cavities  500  which are laterally delimited by the grid structure  104 . The cavities  500  may be formed by etching of the n-type material  106 , for example. The cavities  500  may have uniform or non-uniform sizes. 
       FIG.  5 B  shows each one of the cavities  500  filled with a light conversion layer  502  configured to convert a wavelength of light emitted by the semiconductor mesa  102  aligned with the respective cavity  500 . The light conversion layer  502  may be a separate layer for each semiconductor mesa  102  or group of mesas  102 , or a common layer for the semiconductor mesas  102 . In each case, the light conversion layer  502  changes the color of light emit by the LEDs  100 , e.g., from blue light to one or more other colors such as white, green, red, etc. Any suitable material that converts light of one color into another color may be used for the light conversion layer  502 . For example, a rear earth phosphor material embedded in a silicone matrix may be used as the light conversion layer  502 . In this case, the rear earth phosphor material absorbs blue light and converts the light to a white spectrum. A matrix of silicone with any type of suitable light conversion particles inside may be used as the light conversion layer  502 . Other light conversion material options include YAG (yttrium aluminum gallium), garnet, erbium, cerium, gadolinium, quantum dot conversion material, etc. 
       FIGS.  6 A and  6 B  illustrate partial cross-sectional views of another embodiment of a method of producing the optical projection device. The embodiment shown in  FIGS.  6 A and  6 B  is similar to the embodiment illustrated in  FIGS.  5 A and  5 B . Differently, however, some semiconductor mesas  102  are not recessed and the light conversion layer  502  is implemented as a separate light conversion layer  600 ,  602  for each semiconductor mesa  102  recessed below the upper surface  116  of the grid structure  104 . The separate light conversion layer  600  in some of the cavities  500  is configured for a different wavelength conversion than the separate light conversion layer  602  in other ones of the cavities  500 . Accordingly, the optical projection device may be used as a multi-color projector, e.g., as an RGB (red-green-blue) projector. In the case of an RGB projector, the LEDs  100  may be made of GaN and emit blue light, one of the separate light conversion layers  600  may convert blue light to red light and the other separate light conversion layer  602  may convert blue light into green light. In one example, the size of a cavity  500  may depend on the wavelength conversion provided by the separate light conversion layer  600 ,  602  that fills the respective cavity  500 . Accordingly, cavities  500  that provide less efficient wavelength conversion may be made larger than cavities  500  that provide more efficient wavelength conversion to provide a generally uniform response over a wide range of wavelengths with respect to, e.g., eye-sensitivity for different colors or application specific requirements. 
       FIG.  7    illustrates a partial cross-sectional view of another embodiment of the optical projection device. According to this embodiment, the LEDs  100  are discrete semiconductor dies  700 . Each discrete semiconductor die  700  includes a semiconductor mesa  102  that includes an n-type material  106  and a p-type material  108  adjoining at least partly the n-type material  106  to form a light emitting pn junction  110 , e.g., as shown in  FIGS.  1 A and  1 B . In one embodiment, the grid structure  104  includes an electrically insulating material  702  that at least partly covers the edges  701  of the discrete semiconductor dies  700 . The electrically insulating material  702  of the grid structure  104  may be formed, e.g., by depositing the electrically insulating material  702  at least partly on the edges  701  of the discrete semiconductor dies  700 . 
     The conductive material  114  of the grid structure  104  is disposed on the electrically insulating material  702  such that the electrically insulating material  702  separates the discrete semiconductor dies  700  from the conductive material  114  of the grid structure  104 . For example, the conductive material  114  may be deposited in the gap between discrete semiconductor dies  700  after the electrically insulating material  702  is formed. The conductive material  114  of the grid structure  104  may electrically interconnect the n-type material  106  of the semiconductor mesas  102  within each discrete semiconductor die  700  by extending onto part of the top surface  704  of each discrete semiconductor die  700 . 
     The electrically insulating material  702  covering the edges of the discrete semiconductor dies  700  may comprise, e.g., silicone with titanium oxide particles, oxide and/or nitride, etc. The conductive material  114  of the grid structure  104  instead may fill the entire lateral gap between adjacent discrete semiconductor dies  700 . For example, the conductive material  114  of the grid structure  104  may comprise, e.g., Cu with an Ag sidewall plating. 
     The conductive material  114  of the grid structure  104  may not occupy the entire lateral gap between adjacent discrete semiconductor dies  700 . In this case, the grid structure  104  may further include a fill material  706  that occupies the remaining space between adjacent ones of the discrete semiconductor dies  700  that is unoccupied by the conductive material  114  and the electrically insulating material  702 .  FIG.  7    illustrates an enlarged view of such an embodiment of the grid structure  104  between two adjacent discrete semiconductor dies  700 . In one embodiment, the electrically insulating material  702  covering the edges of the discrete semiconductor dies  700  comprises oxide or nitride, the conductive material  114  of the grid structure  114  comprises Ag, and the fill material  706  comprises Cu or silicone with filler particles. A fixing material  708  such as a molding compound, epoxy, etc. may be provided to secure the discrete semiconductor dies  700  in place. 
       FIG.  8    illustrates a partial cross-sectional view of another embodiment of the optical projection device. According to this embodiment, and within process tolerances, the semiconductor mesas  102  are coplanar with the upper surface  116  of the grid structure  104  and the optical projection device further includes a separate light conversion layer  800  arranged on at least some of the semiconductor mesas  102 . Each separate light conversion layer  800  converts a wavelength of light emitted by the semiconductor mesa  102  aligned with the respective separate light conversion layer  800 . 
     In the case of the semiconductor mesas  102  being coplanar (within process tolerances) with the upper surface  116  of the grid structure  104 , the separate light conversion layers  800  may be formed on the emission surface  404  of the n-type material  106  of the semiconductor mesas  106  without having to etch cavities into the semiconductor mesas  106 . Any suitable material that converts light of one color into another color may be used for the separate light conversion layers  800 . For example, a rear earth phosphor material embedded in a silicone matrix may be used as one or more of the separate light conversion layers  800 . In this case, the rear earth phosphor material absorbs blue light and converts the light to a white spectrum. A matrix of silicone with any type of suitable light conversion particles inside may be used as one or more of the separate light conversion layers  800 . Other light conversion material options include YAG (yttrium aluminum gallium), garnet, gadolinium, quantum dot conversion material, etc. 
     An isolation structure  802  laterally surrounds each of the separate light conversion layers  800  and blocks optical crosstalk between the separate light conversion layers  800 . In one embodiment, the isolation structure  802  includes a wall made of an electrically insulating material  804  that blocks optical crosstalk between the separate light conversion layers  800  and a metal or metal alloy  806  coating the electrically insulating material  804 . For example, the electrically insulating material  804  may be a photoresist such as SU-8 or hybrid-polymer such as ormocer (organically modified ceramic). 
       FIG.  9    illustrates a partial cross-sectional view of different embodiments of forming the open grid  300  shown in  FIG.  3 C . As previously explained herein, the open grid  300  may be formed by etching a grid of intersecting trenches  302  into the n-type material  106  of the semiconductor wafer such that the grid of intersecting trenches  302  laterally separates the semiconductor mesas  102  from one another. The grid etching process may result in trenches  302  of different depth. Accordingly, some trenches  302  may terminate above the dielectric material  126  such that some semiconductor material remains between the trench bottom and the dielectric material  126 . Other trenches  302  may terminate at the dielectric material  126  such that no semiconductor material remains between the trench bottom and the dielectric material  126 . Still other trenches  302  may extend into and terminate within the dielectric material  126 . 
     As previously described herein, the optical projection device may be produced using a semiconductor wafer with epitaxially grown layers of III/V semiconductors that are patterned on the p-side in a way that yields small mesa structures. These small mesa structures are electrically connected to a pixel-specific contact on, e.g., on a CMOS wafer, e.g., by soldering. Subsequently, on the n-side a grid structure is etched down to the underlying dielectric. The etching may be performed by wet etch or by dry etch and an angle of bevel may be set with a tapering of the structure towards the emission side. Subsequently, the structure is filled with a metal that is reflective and electrically conductive. For example, for blue and green light, silver is suitable; for red light, gold is suitable. The grid structure is laterally beside the actual pixel array connected to the n-contact and the cathode conductor on the driver device, respectively. Accordingly, the grid structure supports good electron conduction of the n-epi into the depth of the LED array. With the help of the grid structure, the LED array comprises separated emission areas that do not comprise any waveguide connection between the single elements. Within the LED grid array, single pixel areas may be etched subsequently in a way that defines cavities that may be filled with light conversion material, e.g., quantum dot materials in a silicone matrix. A micro-LED array produced in this way has a plurality of separated point light sources that may be mapped optimally and rich in contrast. Instead of a CMOS driver chip, a TFT panel (e.g., glass substrate) or a simple substrate with electrically conducting supplies for a simple passive matrix triggering may be used. A flexible glass substrate or a polymer foil carrier with applied electrical conductor tracks and vias also may be used for receiving the optical projection device. 
     The embodiments described herein may provide energy saving and mitigation of energy use, e.g., by reducing the size of the LED cells included in an optical projection device by about 50% and by improving current distribution within the area of the LED cells. 
     Although the present disclosure is not so limited, the following numbered examples demonstrate one or more aspects of the disclosure. 
     Example 1. An optical projection device, comprising: a plurality of LEDs (light-emitting diodes), the LEDs each comprising a semiconductor mesa laterally spaced apart from one another by a grid structure, wherein each of the semiconductor mesas comprises an n-type material and a p-type material adjoining at least partly the n-type material, wherein the grid structure at least partly laterally surrounds at least the n-type material of each of the semiconductor mesas, wherein the grid structure comprises a conductive material that electrically interconnects the n-type material of the semiconductor mesas, wherein the grid structure is configured to block optical crosstalk between light emitted by the LEDs. 
     Example 2. The optical projection device of example 1, wherein the plurality of LEDs are part of a semiconductor wafer, wherein the grid structure comprises a grid of intersecting trenches etched into the semiconductor wafer such that the grid of intersecting trenches laterally separates the semiconductor mesas at least partly from one another, and wherein the conductive material of the grid structure fills the grid of intersecting trenches. 
     Example 3. The optical projection device of example 2, wherein the grid structure contacts an n-type region of the semiconductor wafer that is laterally spaced apart from the semiconductor mesas, and wherein the n-type region is connected to a cathode electrode of the optical projection device. 
     Example 4. The optical projection device of example 2 or 3, wherein the grid structure contacts a metal region of the semiconductor wafer that is laterally spaced apart from the semiconductor mesas, and wherein the metal region is connected to a cathode electrode of the optical projection device. 
     Example 5. The optical projection device of example 1, wherein the plurality of LEDs are discrete semiconductor dies, wherein the grid structure comprises an electrically insulating material that at least partly covers edges of the discrete semiconductor dies, wherein the conductive material of the grid structure is disposed on the electrically insulating material such that the electrically insulating material separates the discrete semiconductor dies from the conductive material of the grid structure. 
     Example 6. The optical projection device of example 5, wherein the grid structure comprises a fill material that fills a remaining space between adjacent ones of the discrete semiconductor dies that is unoccupied by the conductive material and the electrically insulating material. 
     Example 7. The optical projection device of example 6, wherein the electrically insulating material comprises oxide or nitride, wherein the conductive material comprises Ag, and wherein the fill material comprises Cu or silicone with filler particles. 
     Example 8. The optical projection device of any of examples 1 through 7, wherein the conductive material of the grid structure comprises Ag. 
     Example 9. The optical projection device of any of examples 1 through 7, wherein the conductive material of the grid structure is selected from the group consisting of: Al; Au; rhodium; and titanium oxide. 
     Example 10. The optical projection device of any of examples 1 through 9, wherein the grid structure has a negative taper. 
     Example 11. The optical projection device of example 10, wherein the negative taper of the grid structure is in a range of 1 to 15 degrees relative to a normal projection onto the semiconductor mesas. 
     Example 12. The optical projection device of any of examples 1 through 11, wherein at least some of the semiconductor mesas are recessed below an upper surface of the grid structure to form cavities which are laterally delimited by the grid structure, and wherein each one of the cavities is filled with a light conversion layer configured to convert a wavelength of light emitted by the semiconductor mesa aligned with the respective cavity. 
     Example 13. The optical projection device of example 12, wherein the cavities have non-uniform sizes. 
     Example 14. The optical projection device of example 12 or 13, wherein the light conversion layer is a separate light conversion layer for each semiconductor mesa recessed below the upper surface of the grid structure, and wherein the separate light conversion layer in some of the cavities is configured for a different wavelength conversion than the separate light conversion layer in other ones of the cavities. 
     Example 15. The optical projection device of any of examples 1 through 14, wherein the semiconductor mesas are coplanar with an upper surface of the grid structure, the optical projection device further comprising: a separate light conversion layer arranged on at least some of the semiconductor mesas and configured to convert a wavelength of light emitted by the semiconductor mesa aligned with the respective separate light conversion layer; and an isolation structure laterally surrounding each of the separate light conversion layers and configured to block optical crosstalk between the separate light conversion layers. 
     Example 16. The optical projection device of example 15, wherein the isolation structure comprises: a wall made of an electrically insulating material and configured to block optical crosstalk between the separate light conversion layers; and a metal or metal alloy coating the electrically insulating material. 
     Example 17. The optical projection device of example 15 or 16, wherein the electrically insulating material is a photoresist. 
     Example 18. The optical projection device of any of examples 1 through 17, further comprising: an individual anode electrode connected to the p-type region of each one of the semiconductor mesas; and a common cathode electrode, wherein the conductive material of the grid structure electrically connects the common cathode electrode to the n-type region of a group of the semiconductor mesas. 
     Example 19. The optical projection device of example 18, further comprising: a driver device configured to drive individual ones of the LEDs, wherein each of the individual anode electrodes is connected to a corresponding anode electrode of the driver device, wherein the common cathode electrode is connected to a cathode electrode of the driver device. 
     Example 20. The optical projection device of example 18 or 19, wherein the driver device is a CMOS (complementary metal-oxide-semiconductor) device, and wherein the semiconductor mesas comprise III/V semiconductor material. 
     Example 21. A method of producing an optical projection device, the method comprising: providing a plurality of LEDs (light-emitting diodes), the LEDs each comprising a semiconductor mesa laterally spaced apart from one another by an open grid , each of the semiconductor mesas comprising an n-type material and a p-type material adjoining the n-type material; and forming a grid structure in the open grid and that at least partly laterally surrounds at least the n-type material of each of the semiconductor mesas, wherein the grid structure comprises a conductive material that electrically interconnects the n-type material of the semiconductor mesas, wherein the grid structure is configured to block optical crosstalk between light emitted by the LEDs. 
     Example 22. The method of example 21, wherein the plurality of LEDs are provided as part of a semiconductor wafer, and wherein forming the grid structure comprises: etching a grid of intersecting trenches into the semiconductor wafer such that the grid of intersecting trenches laterally separates the semiconductor mesas from one another; filling the grid of intersecting trenches with the conductive material. 
     Example 23. The method of example 21, wherein the plurality of LEDs are provided as discrete semiconductor dies, and wherein forming the grid structure comprises: covering at least partly edges of the discrete semiconductor dies with an electrically insulating material; and depositing the conductive material of the grid structure on the electrically insulating material such that the electrically insulating material separates the discrete semiconductor dies from the conductive material of the grid structure. 
     Example 24. The method of example 23, wherein forming the grid structure further comprises: filling a remaining space between adjacent ones of the discrete semiconductor dies that is unoccupied by the conductive material and the electrically insulating material. 
     Example 25. The method of any of examples 21 through 24, further comprising: recessing at least some of the semiconductor mesas below an upper surface of the grid structure to form cavities which are laterally delimited by the grid structure; and filling each one of the cavities with a light conversion layer configured to convert a wavelength of light emitted by the semiconductor mesa aligned with the respective cavity. 
     Example 26. The method of any of examples 21 through 24, wherein the semiconductor mesas are coplanar with an upper surface of the grid structure, the method further comprising: forming a separate light conversion layer on at least some of the semiconductor mesas and configured to convert a wavelength of light emitted by the semiconductor mesa aligned with the respective separate light conversion layer; and laterally surrounding each of the separate light conversion layers by an isolation structure configured to block optical crosstalk between the separate light conversion layers. 
     Terms such as “first”, “second”, and the like, are used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description. 
     As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.