METHOD AND DEVICE FOR PICKING UP AND DEPOSITING OPTOELECTRONIC SEMICONDUCTOR CHIPS

Abstract

A method of picking up and depositing optoelectronic semiconductor chips comprises generating electron-hole pairs in optoelectronic semiconductor chips, thereby generating a dipole electric field in the vicinity of the respective optoelectronic semiconductor chip, generating an electric field by a pick-up tool, and picking up the optoelectronic semiconductor chips during or after generation of the electron-hole pairs by the pick-up tool and depositing them at predetermined locations.

Claims

1. A method for picking up and depositing optoelectronic semiconductor chips, comprising: wherein electron-hole pairs are generated in optoelectronic semiconductor chips, and thereby an electric dipole field is generated in the vicinity of the respective optoelectronic semiconductor chip; wherein a pick-up tool generates an electric field; and wherein the optoelectronic semiconductor chips are picked up by the pick-up tool during or after the generation of the electron-hole pairs and deposited at predetermined positions.

2. The method according to claim 1, wherein the optoelectronic semiconductor chips are LEDs.

3. The method according to claim 1, wherein the optoelectronic semiconductor chips are irradiated with light having a predetermined wavelength or range of wavelengths to generate the electron-hole pairs.

4. The method according to claim 3, wherein the light for generating the electron-hole pairs is incident on the optoelectronic semiconductor chips through the pick-up tool.

5. The method according to claim 3, wherein the optoelectronic semiconductor chips are arranged on a carrier and the light for generating the electron-hole pairs is incident on the optoelectronic semiconductor chips through the carrier.

6. The method according to claim 1, wherein a plurality of optoelectronic semiconductor chips are provided and the electric dipole fields are generated only in selected optoelectronic semiconductor chips of the plurality of optoelectronic semiconductor chips.

7. The method according to claim 1, wherein the pick-up tool generates an electric field only in predetermined areas.

8. The method according to claim 1, wherein the pick-up tool comprises a plurality of protrusions on a surface facing the optoelectronic semiconductor chips and the optoelectronic semiconductor chips are picked up by the protrusions of the pick-up tool.

9. The method according to claim 1, wherein at least a region of a surface of the pick-up tool facing the optoelectronic semiconductor chips is flat and the optoelectronic semiconductor chips are picked up with the flat region of the pick-up tool.

10. The method according to claim 1, wherein the pick-up tool is in the form of a cylinder that is rolled over the optoelectronic semiconductor chips to pick up the optoelectronic semiconductor chips.

11. The method according to claim 1, wherein for depositing the optoelectronic semiconductor chips the electric field generated by the pick-up tool is changed.

12. The method according to claim 1, wherein the pick-up tool for picking up the optoelectronic semiconductor chips directly contacts and holds the optoelectronic semiconductor chips by means of Van der Waals forces.

13. An apparatus for picking up and depositing optoelectronic semiconductor chips, comprising: an excitation element for generating electron-hole pairs in optoelectronic semiconductor chips to produce an electric dipole field in the vicinity of the respective optoelectronic semiconductor chip; and a pick-up tool for picking up and depositing the optoelectronic semiconductor chips, the pick-up tool configured to generate an electric field, then pick up the optoelectronic semiconductor chips with the electron-hole pairs generated by the excitation element and deposit the optoelectronic semiconductor chips at predetermined locations.

14. The apparatus according to claim 13, wherein the excitation element is configured to generate light having a predetermined wavelength or range of wavelengths for generating the electron-hole pairs in the semiconductor optoelectronic chips.

15. The apparatus according to claim 14, wherein the excitation element is arranged such that the light for generating the electron-hole pairs is incident on the optoelectronic semiconductor chips through the pick-up tool or through a carrier on which the optoelectronic semiconductor chips are arranged.

16. The apparatus according to claim 13, wherein the pick-up tool comprises a plurality of protrusions on a surface facing the optoelectronic semiconductor chips and the optoelectronic semiconductor chips are picked up by the protrusions of the pick-up tool.

17. The apparatus according to claim 13, wherein at least a region of a surface of the pick-up tool facing the optoelectronic semiconductor chips is planar and the optoelectronic semiconductor chips are picked up with the planar region of the pick-up tool.

18. The apparatus according to claim 13, wherein the receiving tool is in the form of a cylinder which is rolled over the optoelectronic semiconductor chips to receive the optoelectronic semiconductor chips.

Description

[0055] In the following, embodiments of the invention will be explained in more detail with reference to the accompanying drawings. In these schematically show:

[0056] FIGS. 1A to 1D illustrations of a method and an apparatus for picking up and depositing optoelectronic semiconductor chips;

[0057] FIG. 2 an illustration of a further apparatus for picking up and depositing optoelectronic semiconductor chips;

[0058] FIGS. 3A and 3B illustrations of a method for picking up and depositing optoelectronic semiconductor chips by means of a cylindrical pick-up tool;

[0059] FIG. 4 an illustration of a pick-up tool with protrusions for picking up optoelectronic semiconductor chips;

[0060] FIG. 5 an illustration of a pick-up tool with selective irradiation of optoelectronic semiconductor chips;

[0061] FIG. 6 an illustration of a pick-up tool with a flat surface for picking up optoelectronic semiconductor chips;

[0062] FIGS. 7A to 7C illustrations of a method of depositing optoelectronic semiconductor chips; and

[0063] FIGS. 8A to 8C illustrations of various embodiments for generating an electric field through the pick-up tool.

[0064] In the following detailed description, reference is made to the accompanying drawings, which form a part of this description and in which are shown, for illustrative purposes, specific embodiments in which the invention may be practiced. Since components of embodiments may be positioned in a number of different orientations, the directional terminology is for illustrative purposes and is not limiting in any way. It is understood that other embodiments may be used and structural or logical changes may be made without departing from the scope of protection. It is understood that the features of the various embodiments described herein may be combined, unless specifically indicated otherwise. Therefore, the following detailed description is not to be construed in a limiting sense. In the figures, identical or similar elements are provided with identical reference signs where appropriate.

[0065] FIG. 1A schematically shows an apparatus 10 for picking up and depositing optoelectronic semiconductor chips as an example embodiment according to the invention.

[0066] In the present embodiment, the optoelectronic semiconductor chips are formed as LEDs 11 and are spaced apart from each other on a carrier 12.

[0067] The apparatus 10 comprises a pick-up tool 13, an excitation element 14, and a voltage source 15.

[0068] The excitation element 14 emits light 16 with which the LEDs 11 are irradiated. The light 16 emitted by the excitation element 14 includes wavelengths that generate electron-hole pairs in the optically active region of the LEDs 11 by excitation. The electron-hole pairs cause electrostatic polarization within the LEDs 11, thereby generating an electric dipole field in the vicinity of the respective LED 11.

[0069] In the present embodiment, the pick-up tool 13 is arranged between the excitation element 14 and the LEDs 11. The pick-up tool 13 is at least partially transparent to the light 16 emitted by the excitation element 14, so that the light 16 can reach the LEDs 11.

[0070] The pick-up tool 13 comprises metal contacts embedded, for example, in polydimethylsiloxane (PDMS for short) or other suitable material. The metal contacts are connected to the voltage source 15. An electrostatic field can be generated via a voltage across the metal contacts.

[0071] Further, the pick-up tool 13 comprises protrusions 17 extending from a surface on the underside of the pick-up tool 13 toward the LEDs 11.

[0072] With reference to FIGS. 1A to 1D, a method of picking up and depositing LEDs 11 using the apparatus 10 will be described below as an embodiment according to the invention.

[0073] The light 16 emitted from the excitation element 14 causes excitation and a resulting electrostatic polarization in the LEDs 11. At the same time, the pick-up tool 13 is charged by means of the voltage source 15 in such a way as to cause an attractive interaction between the pick-up tool 13 and the LEDs 11.

[0074] The pick-up tool 13 is moved down toward the LEDs 11 until the protrusions 17 are in contact with the LEDs 11 below. In the present embodiment, every other LED 11 is in contact with one of the protrusions 17.

[0075] As FIG. 1B shows, the pick-up tool 13 is then lifted together with the LEDs 11 adhering to the protrusions 17. FIG. 1C shows an enlarged section of FIG. 1B. FIG. 1C shows the electrostatic charge of the pick-up tool 13 and the polarization of the LEDs 11. For simplicity, FIG. 1B and all subsequent figures do not show the excitation element 14 or the voltage source 15.

[0076] LEDs 11 located between the protrusions 13 are not lifted by the pick-up tool 13. Further, LEDs 11 in which the light 16 emitted from the excitation element 14 causes little or no polarization due to defects in the LEDs 11 are not lifted. These LEDs 11 are shown with a dark background in FIGS. 1A to 1C. The lower polarization compared to intact LEDs 11 allows LEDs 11 with corresponding defects to be sorted out without having to test the LEDs 11 beforehand.

[0077] Subsequently, as shown in FIG. 1D, the LEDs 11 are transferred to a desired location by means of the pick-up tool 13 and deposited there.

[0078] FIG. 2 schematically shows an apparatus 20 for picking up and depositing optoelectronic semiconductor chips as another example of an embodiment according to the invention. The apparatus 20 shown in FIG. 2 is largely identical to the apparatus 10 of FIG. 1A. The difference is that the excitation element 14 in FIG. 2 is arranged below the carrier 12 on which the LEDs 11 are located. In this case, the support 14 must be at least partially transparent to the light 16 emitted by the excitation element 14 in order for photoluminescence excitation to occur in the LEDs 11.

[0079] FIG. 3A schematically shows a cylindrical pick-up tool 13, which may be shaped like the drum of a laser printer. The pick-up tool 13 is electrostatically charged such that an attractive interaction exists between the surface of the pick-up tool 13 and the LEDs 11 located thereunder due to the polarization caused by the photoluminescence excitation.

[0080] As shown in FIG. 3B, the cylindrical pick-up tool 13 is rolled over the support 12, picking up those LEDs 11 in which sufficient polarization has been produced by the incident light 16.

[0081] FIG. 4 schematically shows a pick-up tool 13 with protrusions 17 on its underside extending in the direction of the LEDs 11 arranged below the pick-up tool 13. The light 16 emitted by the excitation element 14, which is not shown in FIG. 4, falls through the pick-up tool 13 onto the LEDs 11.

[0082] To allow the passage of the light 16, the receiving tool 13 may be made of a material that is at least partially transparent to the light 16, or appropriate passage openings or light guides may be incorporated into the receiving tool 13.

[0083] FIG. 5 shows the pick-up tool 13 of FIG. 4, but in FIG. 5 only certain LEDs 11 are selectively irradiated with the light 16, for example every second LED 11. To make this possible, corresponding through-holes or light guides may be integrated into the pick-up tool 13, or a corresponding shading mask may be provided to allow the light 16 to fall only on the predetermined LEDs 11. As a result, only the LEDs 11 irradiated with the light 16 are excited to photoluminescence and only these LEDs 11 can be picked up by the pick-up tool 13, provided that they form a sufficient polarization due to the photoluminescence excitation.

[0084] FIG. 6 schematically shows a pick-up tool 13 having a continuous flat surface 21 on its underside. The flat surface 21 makes it possible to pick up LEDs 11 arranged in different patterns and/or at different distances.

[0085] Furthermore, shading elements, for example a mask, may be provided to selectively excite only certain LEDs 11 to photoluminescence.

[0086] FIGS. 7A to 7C show the apparatus 10 during deposition of the LEDs 11. After picking up the LEDs 11 shown in FIGS. 1A to 1D, the pick-up tool 13 is transferred to a board shown in FIG. 7A, on which some of the LEDs 11 are to be mounted.

[0087] By means of the voltage source 15 shown in FIG. 7B, the electrostatic charge of the pick-up tool 13 is changed such that the attractive interaction between the pick-up tool 13 and the LEDs 11 is reduced or converted into a repulsive interaction. By means of the individually controllable metal contacts in the pick-up tool, the electrical charge in certain areas of the pick-up tool can be changed in the desired manner so that only a predetermined number of the LEDs 11 are deposited on the circuit board 22. The pick-up tool 13 is then removed from the circuit board 22, as shown in FIG. 7C. The LEDs 11 remaining on the pick-up tool 13 may be removed or deposited elsewhere, for example on a cleaning adhesive strip.

[0088] FIGS. 8A to 8C schematically illustrate various options for how an electric field can be generated by the pick-up tool 13. The field lines 23 shown in FIGS. 8A to 8C indicate the direction and strength of the electric field at the respective location.

[0089] In the embodiment shown in FIG. 8A, charges are located in the protrusions 17 of the pick-up tool 13. The counter charges are located in the vicinity of the pick-up tool 13. This results in an electric field in the vicinity of each of the protrusions 17 that is similar to the field of a point charge.

[0090] In FIG. 8B, dipole charges are located in the pick-up tool 13 such that the electric field strength at the tips of the bumps 17 is particularly large.

[0091] In FIG. 8C, the protrusions 17 of the pick-up tool 13 are electrically charged and the counter charges are arranged below the carrier 12, so that the LEDs 11 to be picked up are located between the pick-up tool 13 and the counter charges and thus within the electric field.

[0092] The electric fields generated by means of the pick-up tool 13 should not be homogeneous in order to exert an effective force on the dipoles of the LEDs 11 so that they can be picked up by the support 12.

[0093] FIGS. 8A to 8C also show electric field lines 24 of the LEDs 11 generated by the excitation. The interaction of the field lines 24 of the LEDs 11 with the field lines 23 of the pick-up tool 13 is not shown for simplicity.

LIST OF REFERENCE SIGNS

[0094] 10 Apparatus [0095] 11 LED [0096] 12 Carrier [0097] 13 Pick-up tool [0098] 14 Excitation element [0099] 15 Voltage source [0100] 16 Light [0101] 17 Survey [0102] 20 Apparatus [0103] 21 Surface [0104] 22 Board [0105] 23 Field line of the pick-up tool [0106] 24 Field line of the semiconductor chip