Curing pre-applied and laser-ablated underfill via a laser

Abstract

The invention is directed towards enhanced systems and methods for employing a pulsed photon (or EM energy) source, such as but not limited to a laser, to electrically couple, bond, and/or affix the electrical contacts of a semiconductor device to the electrical contacts of another semiconductor devices. Full or partial rows of LEDs are electrically coupled, bonded, and/or affixed to a backplane of a display device. The LEDs may be μLEDs. The pulsed photon source is employed to irradiate the LEDs with scanning photon pulses. The EM radiation is absorbed by either the surfaces, bulk, substrate, the electrical contacts of the LED, and/or electrical contacts of the backplane to generate thermal energy that induces the bonding between the electrical contacts of the LEDs' electrical contacts and backplane's electrical contacts. The temporal and spatial profiles of the photon pulses, as well as a pulsing frequency and a scanning frequency of the photon source, are selected to control for adverse thermal effects.

What is claimed is: 
     
         1 . A method for coupling a semiconductor device to a target substrate, wherein the semiconductor device includes a first surface and a first contact disposed on the first surface, the target substrate includes a second surface and a second contact disposed on the second surface, and the method comprises:
 depositing uncured underfill (UF) material on the second surface, wherein the uncured UF material substantially covers the second surface and substantially encapsulates the second contact;   applying first thermal energy to the uncured UF material to pre-cure the uncured UF material;   irradiating an excess portion of the pre-cured UF material with a first photon beam to remove the excess portion of the pre-cured UF material and form a planar surface of the pre-cured UF material that at least partially exposes a distal portion of the second contact;   positioning the semiconductor device proximate to the target substrate to form a spatial alignment of the first contact with the second contact, wherein the first and the second surfaces are opposed surfaces, and the at least partially exposed distal portion of the second contact is adjacent a distal portion of the first contact;   forming an electrical coupling between the semiconductor device and the target substrate by bonding the at least partially exposed distal portion of the second contact to the adjacent distal portion of the first contact; and   curing the pre-cured UF material, wherein the cured UF material mechanically stabilizes the electrical coupling between the semiconductor device and the target substrate.   
     
     
         2 . The method of  claim 1 , wherein the uncured UF material is deposited via at least one of a spin coating process, a dip coating process, a doctor blading process, or a spray coating process. 
     
     
         3 . The method of  claim 1 , wherein the first thermal energy is induced by a second photon beam irradiating the excess portion of the pre-cured UF material, and the second photon beam includes one of an ultraviolet (UV) photon beam or an infrared (IR) photon beam. 
     
     
         4 . The method of  claim 1 , wherein the first photon beam is scanned across the excess portion of pre-cured UF material to planarize the planar surface of the pre-cured UF material. 
     
     
         5 . The method of  claim 1 , wherein bonding the at least partially exposed distal portion of the second contact to the adjacent distal portion of the first contact is induced by second thermal energy generated by a second photon beam irradiating at least one of the semiconductor device or the target substrate. 
     
     
         6 . The method of  claim 5 , wherein the second photon beam includes a photon pulse with a temporal profile that is selected to control thermal effects associated with the second thermal energy. 
     
     
         7 . The method of  claim 1 , wherein bonding the at least partially exposed distal portion of the second contact to the adjacent distal portion of the first contact is induced by a thermocompression bonding process. 
     
     
         8 . The method of  claim 1 , wherein an anaerobic adhesive is employed to cure the pre-cured UF material. 
     
     
         9 . The method of  claim 1 , wherein a moisture-absorbing process is employed to cure the pre-cured UF material. 
     
     
         10 . The method of  claim 1 , wherein the semiconductor device is a light-emitting diode (LED) with feature sizes that are less than 100 micrometers (μm) and the target substrate is a backplane of a display device. 
     
     
         11 . A system for coupling a semiconductor device to a target substrate, wherein the semiconductor device includes a first surface and a first contact disposed on the first surface, the target substrate includes a second surface and a second contact disposed on the second surface, the system comprising:
 an underfill (UF) deposition apparatus that deposits uncured underfill (UF) material on the second surface, wherein the uncured UF material substantially covers the second surface and substantially encapsulates the second the second contact;   an ablation apparatus that removes an excess portion of the pre-cured UF material and forms a planar surface of the pre-cured UF material that at least partially exposes a distal portion of the second contact;   a pick and place head (PPH) that positions the semiconductor device proximate to the target substrate to form a spatial alignment of the first contact with the second contact, wherein the first and the second surfaces are opposed surfaces, and the at least partially exposed distal portion of the second contact is adjacent a distal portion of the first contact;   an electrical coupling apparatus that forms an electrical coupling between the semiconductor device and the target substrate by bonding the at least partially exposed distal portion of the second contact to the adjacent distal portion of the first contact; and   a curing apparatus that cures the pre-cured UF material, wherein the cured UF material mechanically stabilizes the electrical coupling between the semiconductor device and the target substrate.   
     
     
         12 . The system of  claim 11 , wherein the UF deposition apparatus includes at least one of a spin coating apparatus, a dip coating apparatus, a doctor blading apparatus, or a spray coating apparatus. 
     
     
         13 . The system of  claim 11 , wherein the UF pre-curing apparatus includes a photon source that irradiates the pre-cured UF material with emitted photons of wavelengths are within a range that is between an ultraviolet (UV) band of an electromagnetic (EM) spectrum and an infrared (IR) band of the EM spectrum. 
     
     
         14 . The system of  claim 11 , wherein the UF pre-curing apparatus employs a thermal UF curing process. 
     
     
         15 . The system of  claim 11 , wherein the ablation apparatus includes a scanning laser beam that is scanned across the excess portion of pre-cured UF material to planarize the planar surface of the pre-cured UF material. 
     
     
         16 . The system of  claim 11 , wherein the electrical coupling apparatus transmits a photon pulse with a temporal profile that is selected to control thermal effects associated with thermal energy induced by the photon pulse, the thermal energy bonding the at least partially distal portion of the second contact to the adjacent distal portion of the first contact. 
     
     
         17 . The system of  claim 14 , wherein the curing apparatus employs a room temperature UF curing process. 
     
     
         18 . A display device, comprising:
 a semiconductor device that includes a first surface and a first contact disposed on the first surface; and   a target substrate that includes a second surface and a second contact disposed on the second surface, and   wherein the display device was assembled by a method comprising:
 depositing uncured underfill (UF) material on the second surface, wherein the uncured UF material substantially covers the second surface and substantially encapsulates the second contact; 
 applying first thermal energy to the uncured UF material to pre-cure the uncured UF material; 
 irradiating an excess portion of the pre-cured UF material with a first photon beam to remove the excess portion of the pre-cured UF material to form a planar surface of the pre-cured UF material that at least partially exposes a distal portion of the second contact; 
 positioning the semiconductor device proximate to the target substrate to form a spatial alignment of the first contact with the second contact, wherein the first and the second surfaces are opposed surfaces, and the at least partially exposed distal portion of the second contact is adjacent a distal portion of the first contact; 
 forming an electrical coupling between the semiconductor device and the target substrate by bonding the at least partially exposed distal portion of the second contact to the adjacent distal portion of the first contact; and 
 curing the pre-cured UF material, wherein the cured UF material mechanically stabilizes the electrical coupling between the semiconductor device and the target substrate. 
   
     
     
         19 . The display device of  claim 18 , wherein the display device is included in a head-mounted device that is at least one of a virtual-reality device, an augmented-reality device, or a mixed-reality device. 
     
     
         20 . The display device of  claim 18 , wherein at least one of the first contact or the second contact is comprised of nanoporous gold (NPG).