US 10,768,515 B2 · Method for manufacturing ultra-dense LED projector using thinned gallium nitride

Abstract

A small projector uses an ultra-dense array of gallium nitride (GaN) LEDs. However, epitaxial growth of GaN typically produces a GaN region that is Sum or thicker. To achieve high pixel density, the LEDs have small area, so the resulting LED structures are tall and skinny. This is undesirable because it makes further processing more difficult and has higher optical losses. As a result, it is beneficial to reduce the thickness of the GaN region. In one approach, a wafer with the GaN region on substrate is bonded to a backplane wafer containing LED driver circuits. The substrate is then separated from the GaN region, exposing a buffer layer of the GaN region. The GaN region is thinned and then patterned into individual LEDs. Typically, the buffer layer is removed entirely.

Claims24

Dependent claims

A method for manufacturing a femtoprojector display, the method comprising:

attaching a frontplane die to a backplane die, the backplane die comprising an array of LED driver circuits on a backplane substrate, and the frontplane die comprising a gallium nitride region grown on a frontplane substrate, where attaching the frontplane die to the backplane die comprises bonding a metal layer on the frontplane die to a metal layer on the backplane die, and where the bonding uses a bonding agent selected from aluminum;
indium tin oxide;
aluminum-doped zinc oxide;
aluminum with a surface coating of silicon, germanium or titanium;
Sn solder and In solder;
removing the frontplane substrate;
thinning the gallium nitride region;
and
patterning the gallium nitride region into individual LED pillars having an active region of width not more than 2 um, where thinning the gallium nitride region reduces a height of the individual LED pillars as measured from the active region to a top of the gallium nitride region to less than 3 um.

6 more elements

A method for manufacturing a femtoprojector display, the method comprising:

attaching a frontplane die to a backplane die, the backplane die comprising an array of LED driver circuits on a backplane substrate, and the frontplane die comprising a gallium nitride region grown on a frontplane substrate;
removing the frontplane substrate;
thinning the gallium nitride region;
and
patterning the gallium nitride region into individual LED pillars having an active region of width not more than 2 um, where thinning the gallium nitride region reduces a height of the individual LED pillars as measured from the active region to a top of the gallium nitride region to less than 3 um;
where patterning the gallium nitride region into individual LED pillars comprises:
lithographically masking areas of the gallium nitride region to define the individual LED pillars;
and
etching trenches into areas of the gallium nitride region that are not masked;
and
without any lithography steps:
passivating sidewalls of the individual LED pillars;
and
forming electrical contacts to top contacts of the individual LED pillars.

11 more elements

Dependencies are inferred from the claim text.

Method for manufacturing ultra-dense LED projector using thinned gallium nitride

Life of this patent

Method for manufacturing ultra-dense LED projector using thinned gallium nitride

Life of this patent

Abstract

Claims24