METHOD AND PROCESS FOR DEPOSITION OF TEXTURED ZINC OXIDE THIN FILMS
A method for sputtering a textured zinc oxide coating onto a substrate by reactive-environment hollow cathode sputtering comprises providing a sputter reactor that has a cathode channel and a flow exit end. The cathode channel allows a gas stream to flow therein. This cathode channel is at least partially defined by a channel-defining surface that includes at least one zinc-containing target. A gas is flowed through the channel, such that the gas emerges from the flow exit. A plasma is then generated such that material is sputtered off the channel-defining surface to form a gaseous mixture containing zinc atoms that is transported to the substrate. A reactive gas is then introduced into the sputter reactor so that the reactive gas reacts with the zinc-containing gaseous mixture to form the textured zinc oxide coating.
1 . A method for sputtering a textured zinc oxide coating onto a substrate using a sputter reactor comprising a cathode channel that allows a gas stream to flow therein to a reaction chamber and having a flow exit end, the cathode channel being defined by a channel defining surface, the channel defining surface having at least one zinc containing target, the method comprising:
a) establishing a reaction chamber pressure between 80 and 400 mT;
b) establishing a substrate temperature greater than about 170° C.;
b) flowing a gas through the channel;
c) generating a plasma, wherein material is sputtered off the channel-defining surface to form a zinc-containing gaseous mixture containing target atoms that are transported to the substrate; and
d) introducing a reactive oxygen containing gas into the sputter reactor, the reactive gas reacting with the zinc-containing gaseous mixture to form the textured zinc oxide coating, the textured zinc oxide coating scattering at least 1% of visible light incident thereon.
2 . The method of claim 1 wherein the substrate temperature is from about 170° C. to about 400° C.
3 . The method of claim 1 wherein the substrate temperature is from about 250° C. to about 350° C.
4 . The method of claim 1 wherein textured zinc oxide coating scatters from about 1% to about 75% of visible light incident thereon.
5 . The method of claim 1 wherein textured zinc oxide coating scatters from about 20% to about 60% of visible light incident thereon.
6 . The method of claim 1 wherein textured zinc oxide coating scatters from about 10% to about 20% of visible light incident thereon.
7 . The method of claim 1 wherein textured zinc oxide coating comprises surface features having a size dimension greater than about 0.5 microns.
8 . The method of claim 7 wherein at least 10% of the surface features have a size dimension greater than about 0.5 microns.
9 . The method of claim 7 wherein at least 20% of the surface features have a size dimension greater than about 0.5 microns.
10 . The method of claim 7 wherein at least 30% of the surface features have a size dimension greater than about 0.5 microns.
11 . The method of claim 1 further comprising introducing a dopant into the textured zinc oxide coating.
12 . The method of claim 1 wherein the textured zinc oxide coating have a resistivity is less than 5×10 −3 ohm-cm.
13 . The method of claim 1 wherein the textured zinc oxide coating have a resistivity is less than 1×10 −3 ohm-cm.
14 . The method of claim 1 wherein the textured zinc oxide coating have a resistivity greater than 1×10 −4 ohm-cm.
15 . The method of claim 1 wherein the textured zinc oxide coating has a thickness from 0.5 microns to about 3.0 microns.
16 . The method of claim 1 wherein the textured zinc oxide coating has a thickness from about 1.0 microns to about 3.0 microns.
17 . The method of claim 1 wherein the reactive oxygen containing gas comprises oxygen, water, or a combination thereof.