Abstract:
Light Emitting Diodes (LEDs) (20) are fabricated on a wafer substrate (40) with one or more thick metal layers (28,30) that provide structural support to each LED (20). The streets (33), or lanes, between individual LEDs (20) do not include this metal, and the wafer can be easily sliced/diced into singulated self-supporting LEDs (20). Before singulation, further processes may be applied at the wafer- level; after singulation, these self-supporting LEDs (20) can be picked and placed directly upon a leadframe (210). The leadframe (210) may be molded to provide a particular shape that enhances the light output efficiency and/or facilitates subsequent fabrication processes.
Abstract:
Semiconductor LED layers are epitaxially grown on a patterned surface of a sapphire substrate (10). The patterned surface improves light extraction. The LED layers include a p-type layer and an n-type layer. The LED layers are etched to expose the n-type layer. One or more first metal layers are patterned to electrically contact the p- type layer and the n-type layer to form a p-metal contact (32) and an n-metal contact (33). A dielectric polymer stress-buffer layer (36) is spin-coated over the first metal layers to form a substantially planar surface over the first metal layers. The stress-buffer layer has openings exposing the p-metal contact and the n-metal contact. Metal solder pads (44, 45) are formed over the stress-buffer layer and electrically contact the p-metal contact and the n-metal contact through the openings in the stress-buffer layer. The stress-buffer layer acts as a buffer to accommodate differences in CTEs of the solder pads and underlying layers.
Abstract:
A technique is disclosed for causing the top surfaces of solder bumps on a chip to be in the same plane to ensure a more reliable bond between the chip and a substrate. The chip is provided with solder pads that may have different heights. A dielectric layer is formed between the solder pads. A relatively thick metal layer is plated over the solder pads. The metal layer is planarized to cause the top surfaces of the metal layer portions over the solder pads to be in the same plane and above the dielectric layer. A substantially uniformly thin layer of solder is deposited over the planarized metal layer portions so that the top surfaces of the solder bumps are substantially in the same plane. The chip is then positioned over a substrate having corresponding metal pads, and the solder is reflowed or ultrasonically bonded to the substrate pads.
Abstract:
In one embodiment, a semiconductor device wafer (10) contains electrical components and has electrodes (28) on a first side of the device wafer (10). A transparent carrier wafer (30) is bonded to the first side of the device wafer (10) using a bonding material (32) (e.g., a polymer or metal). The second side of the device wafer (10) is then processed, such as thinned, while the carrier wafer (30) provides mechanical support for the device wafer (10). The carrier wafer (30) is then de-bonded from the device wafer (10) by passing a laser beam (46) through the carrier wafer (30), the carrier wafer (30) being substantially transparent to the wavelength of the beam. The beam impinges on the bonding material (32), which absorbs the beam's energy, to break the chemical bonds between the bonding material (32) and the carrier wafer (30). The released carrier wafer (30) is then removed from the device wafer (10), and the residual bonding material is cleaned from the device wafer (10).
Abstract:
Light Emitting Devices (LEDs) are fabricated on a wafer substrate with one or more thick metal layers that provide structural support to each LED. The streets, or lanes, between individual LEDs do not include this metal, and the wafer can be easily sliced/diced into singulated self-supporting LEDs. Because these devices are self-supporting, a separate support submount is not required. Before singulation, further processes may be applied at the wafer-level; after singulation, these self-supporting LEDs may be picked and placed upon an intermediate substrate for further processing as required. In an embodiment of this invention, protective optical domes are formed over the light emitting devices at the wafer-level or while the light emitting devices are situated on the intermediate substrate.
Abstract:
Thick metal pillars are formed upon light emitting dies while the dies are still on their supporting wafer. A molding compound is applied to fill the space between the pillars on each die, and contact pads are formed atop the pillars. The metal pillars provide electrical contact between the contact pads and the electrical contacts of each light emitting die. The metal pillars maybe formed upon an upper metal layer of each die, and this upper metal layer maybe patterned to provide connections to individual elements within the die.