Method of deposition
In a method for sputter depositing an additive-containing aluminium nitride film containing an additive element like Sc or Y, a first layer of the additive-containing aluminium nitride film is deposited onto a substrate disposed within a chamber by pulsed DC reactive sputtering. A second layer of the additive-containing aluminium nitride film is deposited onto the first layer by pulsed DC reactive sputtering. The second layer has the same composition as the first layer. A gas or gaseous mixture is introduced into the chamber when depositing the first layer. A gaseous mixture comprising nitrogen gas and an inert gas is introduced into the chamber when depositing the second layer. The percentage of nitrogen gas in the flow rate (in sccm) when depositing the first layer is greater than that when depositing the second layer.
1. A method for sputter depositing an additive-containing aluminium nitride film containing an additive element selected from Sc or Y, the method comprising the steps of:
depositing a first layer of the additive-containing aluminium nitride film onto a substrate disposed within a chamber by pulsed DC reactive sputtering, wherein the step of depositing the first layer is performed with an RF bias power above 250 W applied to the substrate, and wherein the first layer is compressive; and
depositing a second layer of the additive-containing aluminium nitride film onto the first layer by pulsed DC reactive sputtering, the second layer having the same composition as the first layer, wherein the step of depositing the second layer is performed with an RF bias power lower than the RF bias power applied during the step of depositing the first layer, and wherein the RF bias power for the step of depositing the second layer is selected so that an overall film stress of the first layer and the second layer is approximately zero;
wherein:
the step of depositing the first layer comprises introducing a gas or gaseous mixture into the chamber at a flow rate (in sccm), and 87-100% of the flow rate (in sccm) is a flow of nitrogen gas;
the step of depositing the second layer comprises introducing a gaseous mixture into the chamber at a flow rate (in sccm), the gaseous mixture comprising nitrogen gas and an inert gas;
the percentage of the nitrogen gas in the flow rate (in sccm) used during the step of depositing the first layer is greater than a percentage of the nitrogen gas in the flow rate (in sccm) used during the step of depositing the second layer whereby the additive-containing aluminium nitride film has a defect density of less than 50 defects per 100 um 2 ; and
the substrate comprises a metallic layer onto which the first layer of the additive-containing aluminium nitride film is deposited.
2. A method according to claim 1 , wherein the additive element is scandium.
3. A method according to claim 1 , wherein the additive element is present in an amount in the range 0.5 At % to 40 At %.
4. The method according to claim 1 , wherein 90-100% of the flow rate (in sccm) used during the step of depositing the first layer is a flow of nitrogen gas.
5. The method according to claim 4 , wherein the flow rate (in sccm) used during the step of depositing the first layer consists essentially of a flow of nitrogen gas only.
6. The method according to claim 1 , wherein the flow of nitrogen gas used during the step of depositing the first layer is in the range 50 to 500 sccm.
7. The method according to claim 1 , wherein the gas or gaseous mixture used during the step of depositing the first layer comprises nitrogen gas and an inert gas.
8. The method according to claim 1 , wherein the chamber has a pressure in the range 2-6 mTorr during the step of depositing the first layer.
9. The method according to claim 1 , wherein the chamber has a pressure in the range 1.5-7.5 mTorr during the step of depositing the second layer.
10. The method according to claim 1 , wherein the first layer has a thickness of less than 70 nm.
11. The method according to claim 1 , wherein the additive-containing aluminium nitride film has a thickness of 0.3 μm or greater; 0.6 μm or greater; or about 1 μm.
12. The method according to claim 1 , wherein the additive-containing aluminium nitride film has a thickness of 2 μm or less.
13. The method according to claim 1 , wherein the step of depositing the second layer is performed with no electrical bias power applied to the substrate.
14. The method according to claim 1 further comprising the step of etching a surface of the substrate prior to the step of depositing the first layer so that the first layer is deposited onto the etched surface of the substrate.
15. The method according to claim 1 wherein the substrate is a silicon substrate.
16. The method according to claim 1 wherein the metallic layer is a molybdenum layer.
17. The method according to claim 16 further comprising the step of depositing the metallic layer onto a substrate precursor.
18. An additive-containing aluminium nitride film produced by the method according to claim 1 .
19. The method according to claim 1 , wherein only one target is used during the pulsed DC reactive sputtering.