SCANDIUM-ALUMINUM ALLOY SPUTTERING TARGETS

1 . A method of manufacturing a sputtering target, comprising:

forming a scandium-aluminum alloy comprising 3-10 at % scandium and 90-97 at % aluminum; and

preparing the scandium-aluminum alloy for use as a sputtering target in plasma deposition equipment.

2 . The method of claim 1 , further comprising measuring a composition of the scandium-aluminum alloy, comparing the measured composition to a desired composition, and adjusting a composition of a subsequent sputtering target according to the comparison.

3 . The method of claim 2 , wherein measuring the composition comprises performing inductively coupled plasma (ICP) mass spectrometry (MS).

4 . The method of claim I, further comprising measuring a microstructure of the scandium-aluminum alloy, comparing the measured microstructure to a desired microstructure, and adjusting a microstructure of a subsequent sputtering target according to the comparison.

5 . The method of claim 4 , wherein the measured microstructure comprises a grain size of ScAl 3 within the sputtering target.

6 . The method of claim 5 , wherein adjusting the microstructure comprises modifying a process parameter to reduce the average grain size to less than 40 μm.

7 . The method of claim 1 , further comprising measuring scandium segregation of the scandium-aluminum alloy, comparing the measured segregation to a desired segregation, and adjusting a segregation of a subsequent sputtering target according to the comparison.

8 . The method of claim 1 , wherein forming the scandium-aluminum alloy comprises:

melting precursor materials comprising pure scandium and pure aluminum;

fast casting the melted precursor materials to produce a scandium aluminum alloy ingot;

forging or rolling the scandium aluminum alloy ingot;

heat treating the forged or rolled scandium aluminum alloy ingot; and

bonding and machining the heat treated scandium aluminum alloy ingot.

9 . The method of claim 8 , wherein forming the scandium-aluminum alloy further comprises:

performing inductively coupled plasma (ICP) relative intensity analysis on the scandium aluminum alloy ingot to determine its scandium content.

10 . The method of claim 9 , further comprising adjusting at least one process parameter for the manufacture of a subsequent sputtering target according to the determined scandium content.

11 . A method of manufacturing an acoustic resonator structure, comprising:

in an atmosphere containing nitrogen gas, performing a sputtering process using a sputtering target comprising a scandium aluminum alloy having 3-10 at % scandium and 90-97 at % aluminum.

12 . The method of claim 11 , wherein the sputtering target comprises ScAl 3 with a grain size less than 40 μm .

13 . The method of claim 11 , further comprising:

forming a first electrode on a substrate;

performing the sputtering process to deposit a layer of aluminum scandium nitride (ASN) on the first electrode; and

forming a second electrode on the layer of ASN.

14 . The method of claim 13 , further comprising:

measuring a uniformity of an electromechanical coupling coefficient (kt 2 ) across the layer of ASN; and

adjusting a process parameter used to produce a subsequent sputtering target according to the measurement.

15 . The method of claim 14 , wherein measuring the uniformity comprises performing inductively coupled plasma (ICP) mass spectrometry (MS).

16 . The method of claim 13 , further comprising:

measuring an electromechanical coupling coefficient (kt 2 ) of the layer of ASN;

comparison the measured kt 2 with a kt 2 of at least one other layer of ASN produced by the sputtering target; and

adjusting a process parameter used to produce a subsequent sputtering target according to the comparison.

17 . The method of claim 16 , wherein the process parameter comprises a relative proportion of scandium in precursor materials used to produce a scandium aluminum alloy.

18 . An apparatus, comprising:

a sputtering target comprising an alloy of scandium and aluminum, wherein the alloy has a concentration of 3-10 at % scandium and 90-97 at % aluminum.

19 . The apparatus of claim 18 , wherein the alloy comprises ScAl 3 with a grain size less than 40 μm.

20 . The apparatus of claim 18 , further comprising plasma deposition equipment incorporating the sputtering target.