Method of depositing an aluminum nitride (AlN) thin film
A method of depositing an AlN thin film according to an embodiment of the disclosure comprises: a step of forming an insulating layer on a base substrate; and a step of depositing an AlN thin film on the insulating layer through a sputtering process, wherein the step of depositing the AlN thin film is performed through a continuous deposition type, at lower than a CMOS-compatible process temperature and in a state of applying a bias positive voltage to the base substrate such that the AlN thin film has an adjustable deposition thickness. Therefore, an embodiment of the disclosure is advantageous in that an AlN thin film having excellent piezo characteristics can be obtained at a low process temperature compatible with a CMOS process.
1 . A method of depositing an aluminum nitride (AlN) thin film comprising:
a step of forming an insulating layer on a base substrate;
a step of removing impurities contained in aluminum (Al) used as a sputtering target by performing pre-sputtering process; and
a step of depositing an AlN thin film on the insulating layer through a sputtering process,
wherein the step of depositing the AlN thin film is performed through a continuous deposition type, at a temperature range lower than a CMOS-compatible process temperature, wherein the temperature range is 280° C. to 300° C. and in a state of applying a bias positive voltage to the base substrate such that the AlN thin film has an adjustable deposition thickness configured to be adjusted to a predetermined thickness satisfying vertical growth conditions of an AlN(002) surface of the AlN thin film,
wherein the applied bias positive voltage is a voltage within a range of 8% to 12% of a power applied to a sputter target for depositing AlN thin film through the sputtering process such that the AlN thin film is vertically grown on the insulating layer,
wherein at least one region of a metal electrode is formed on only an upper portion of the AlN thin film, and a lower portion of the AlN thin film is free of contact with the metal electrode,
wherein an oxide film formed on an upper surface of the metal electrode is configured to define three or four regions of the metal electrode
wherein other regions of the metal electrode are directly formed on a top of the insulating layer of the base substrate, and an upper surface of each of the other regions of the metal electrode is partially covered by the oxide film, and
wherein a preset value of the power applied to the sputter target is within a range of 250-300W.
2 . The method of claim 1 , wherein the applied bias positive voltage is a voltage of 10% of the power applied to the sputter target.
3 . The method of claim 1 , wherein the predetermined thickness of the AlN thin film is at least 1 μm or more.
4 . The method of claim 1 , wherein the AlN thin film is used for a piezoelectric micromachined ultrasonic transducers (PMUT) sensor.
5 . A method of depositing an aluminum nitride (AlN) thin film comprising:
a step of forming an insulating layer on a base substrate;
a step of forming a seed layer for growing an AlN thin film on the insulating layer;
a step of removing impurities contained in aluminum (Al) and molybdenum (Mo) used as a sputtering target by performing pre-sputtering process; and
a step of depositing the AlN thin film on the seed layer through a sputtering process,
wherein the step of depositing the AlN thin film is performed through a continuous deposition type, at a temperature range lower than a CMOS-compatible process temperature, wherein the temperature range is 280° C. to 300° C. and in a state of applying a bias positive voltage to the base substrate such that the AlN thin film has an adjustable deposition thickness configured to be adjusted to a predetermined thickness satisfying vertical growth conditions of an AlN(002) surface of the AlN thin film,
wherein the applied bias positive voltage is a voltage within a range of 8% to 12% of a power applied to a sputter target for depositing AlN thin film through the sputtering process such that the AlN thin film is vertically grown on the insulating layer,
wherein at least one region of a metal electrode is formed on only an upper portion of the AlN thin film, and a lower portion of the AlN thin film is free of contact with the metal electrode,
wherein an oxide film formed on an upper surface of the metal electrode is configured to define three or four regions of the metal electrode
wherein other regions of the metal electrode are in direct contact with the insulating layer, and an upper surface of each of the other regions of the metal electrode is partially covered by the oxide film, and
wherein a preset value of the power applied to the sputter target is within a range of 250-300W.
6 . The method of claim 5 , wherein the applied bias positive voltage is a voltage of 10% of the power applied to the sputter target.
7 . The method of claim 5 , wherein the predetermined thickness of the AlN thin film is at least 1 μm or more.
8 . The method of claim 5 , wherein the AlN thin film is used for a piezoelectric micromachined ultrasonic transducers (PMUT) sensor.