*3.1. Composition and Structure of AlScN Films*

The first coatings were performed directly on Si substrates, and the film thickness distribution was ±1.5% at Ø180 mm and ±3% at Ø200 mm. The film composition was determined by EDS. The results are shown in Figure 2. The Sc content of the AlXSc1-XN films was slightly below that of the nominal target composition as given by the manufacturer, especially at a longer distance from the symmetry axis of the magnetron, going as low as 28 at.% Sc at the radial position 100 mm, while being around 29.5 at.% Sc in the inner coating area. These (minor) variations can be attributed to geometric effects such as shadowing of particle flux by the outer plasma shields and the difference in angular distribution of sputtered Al and Sc atoms. The latter effect is expected to be more pronounced at low target–substrate distances (TSD 90 mm) and low pressure, i.e., a high mean free path of atoms.

of atoms.

tion.

of atoms.

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**Figure 2.** EDS measurement of Sc content in AlScN and comparison to the Al0.7Sc0.3 target composi-**Figure 2.** EDS measurement of Sc content in AlScN and comparison to the Al0.7Sc0.3 target composition. Si/Ti/Pt with a 5 nm Ti and 40 nm Pt seed layer for different pulse modes and radial positions. All films were highly c-axis-oriented, with (002) peaks being the main intensity by

low target–substrate distances (TSD 90 mm) and low pressure, i.e., a high mean free path

low target–substrate distances (TSD 90 mm) and low pressure, i.e., a high mean free path

tion. Figure 3 shows the θ–2θ scans of AlScN with 2.5 µm and 0.9 µm thicknesses on Si/Ti/Pt with a 5 nm Ti and 40 nm Pt seed layer for different pulse modes and radial positions. All films were highly c-axis-oriented, with (002) peaks being the main intensity by far. The 2.5 µm-thick films deposited with a more unipolar pulse mode (Su = 90%), revealing that there were also weak peaks of (102) and (103) orientation present, although those had a very small intensity of 1:3500 relative to the (002) peak. On the other hand, the films deposited with a lower share of unipolar pulse mode (Su = 60%) exhibited no (102) or (103) peaks in the inner radial positions, while they appeared only at the edge of the coating area (r = 90 mm), with intensity ratios to the (002) peak being 1/1000 and 1/2000, respectively. The thinner films with 900 nm thickness, on the other hand, exhibited no visible Figure 3 shows the θ–2θ scans of AlScN with 2.5 µm and 0.9 µm thicknesses on Si/Ti/Pt with a 5 nm Ti and 40 nm Pt seed layer for different pulse modes and radial positions. All films were highly c-axis-oriented, with (002) peaks being the main intensity by far. The 2.5 µm-thick films deposited with a more unipolar pulse mode (S<sup>u</sup> = 90%), revealing that there were also weak peaks of (102) and (103) orientation present, although those had a very small intensity of 1:3500 relative to the (002) peak. On the other hand, the films deposited with a lower share of unipolar pulse mode (S<sup>u</sup> = 60%) exhibited no (102) or (103) peaks in the inner radial positions, while they appeared only at the edge of the coating area (r = 90 mm), with intensity ratios to the (002) peak being 1/1000 and 1/2000, respectively. The thinner films with 900 nm thickness, on the other hand, exhibited no visible (102) or (103) peaks, regardless of pulse mode or radial position, indicating a high crystalline quality over the whole coating area for the thinner films, similar to results for thickness-dependent occurrences of AOG reported in [12]. far. The 2.5 µm-thick films deposited with a more unipolar pulse mode (Su = 90%), revealing that there were also weak peaks of (102) and (103) orientation present, although those had a very small intensity of 1:3500 relative to the (002) peak. On the other hand, the films deposited with a lower share of unipolar pulse mode (Su = 60%) exhibited no (102) or (103) peaks in the inner radial positions, while they appeared only at the edge of the coating area (r = 90 mm), with intensity ratios to the (002) peak being 1/1000 and 1/2000, respectively. The thinner films with 900 nm thickness, on the other hand, exhibited no visible (102) or (103) peaks, regardless of pulse mode or radial position, indicating a high crystalline quality over the whole coating area for the thinner films, similar to results for thickness-dependent occurrences of AOG reported in [12].

 **Figure 3.** θ–2θ scan of 2.5µm (**left**) and 0.9 µm (**right**) AlScN films at different radial positions (25 mm, 45 mm, 90 mm); peaks labeled as Si(400) are the Si substrate peaks by Cu Kα1/2 (69.2°), Cu Kβ<sup>1</sup> (61.7°) and Cu W Lα1 (65.9°); the peaks at 32.2° and 34.2° are the AlScN(002) Peaks by Cu Kβ1 and Cu **Figure 3.** θ–2θ scan of 2.5µm (**left**) and 0.9 µm (**right**) AlScN films at different radial positions (25 mm, 45 mm, 90 mm); peaks labeled as Si(400) are the Si substrate peaks by Cu Kα1/2 (69.2◦ ), Cu Kβ<sup>1</sup> (61.7◦ ) and Cu W Lα<sup>1</sup> (65.9◦ ); the peaks at 32.2◦ and 34.2◦ are the AlScN(002) Peaks by Cu Kβ<sup>1</sup> and Cu WLα<sup>1</sup> , as well as Si(200) by Cu Kα<sup>1</sup> at 33.0◦ , respectively.

**Figure 3.** θ–2θ scan of 2.5µm (**left**) and 0.9 µm (**right**) AlScN films at different radial positions (25

From the 2θ position of AlScN (002) peaks in Figure 3, the c-lattice constant was calculated as described in the Methods section. Film stress, e.g., due to energetic particle

pared to stress free values [17]. For c-axis-oriented films, the lattice parameter c increased

bombardment during layer deposition, results in a shift of the c-lattice parameter com-

mm, 45 mm, 90 mm); peaks labeled as Si(400) are the Si substrate peaks by Cu Kα1/2 (69.2°), Cu Kβ<sup>1</sup> (61.7°) and Cu W Lα1 (65.9°); the peaks at 32.2° and 34.2° are the AlScN(002) Peaks by Cu Kβ1 and Cu WLα1, as well as Si(200) by Cu Kα1 at 33.0°, respectively. WLα1, as well as Si(200) by Cu Kα1 at 33.0°, respectively. From the 2θ position of AlScN (002) peaks in Figure 3, the c-lattice constant was calculated as described in the Methods section. Film stress, e.g., due to energetic particle From the 2θ position of AlScN (002) peaks in Figure 3, the c-lattice constant was calculated as described in the Methods section. Film stress, e.g., due to energetic particle bombardment during layer deposition, results in a shift of the c-lattice parameter compared to stress free values [17]. For c-axis-oriented films, the lattice parameter c increased with

increasing in-plane compressive film stress. Additionally, besides the effect due to film stress, the lattice parameters a and c of AlScN increased with the incorporation of scandium into the wurtzite structure. The lattice parameters of AlN are a = 0.31114 nm and c = 0.49792 nm according to ICDD PDF-25-1133. According to calculations by other groups, the a-axis lattice parameter of Al0.7Sc0.3cN should be increased compared to that of AlN by ca. 4.4% to 0.3248–0.3250 nm, and the c-axis lattice parameter should increase by ca. 0.5–1% to 0.5003–0.5027 nm [18,19]. The calculated c-axis values from XRD measurements for different pulse modes and radial positions are shown in Figure 4. As can be seen, the mostly unipolar pulse mode (S<sup>u</sup> = 90%) was almost homogenous along the whole radius. Film stress, as calculated with the wafer curvature method on a reference sample, i.e., an AlScN-coated 8 inch Si wafer without any electrode layers, was homogenous over the deposition area and around −700 MPa, therefore compressive. On the other hand, the pulse mode with a lower share of unipolar (S<sup>u</sup> = 60%) was more inhomogeneous, with a 2% bigger c axis in the wafer middle compared to the edge and thus a much higher compressive stress of above 1.5 GPa. This is in line with previous results, revealing higher plasma density near the substrate and higher energetic bombardment of the substrate at a higher share of bipolar pulse mode (see Figure 1, [14]). and c = 0.49792 nm according to ICDD PDF-25-1133. According to calculations by other groups, the a-axis lattice parameter of Al0.7Sc0.3cN should be increased compared to that of AlN by ca. 4.4% to 0.3248–0.3250 nm, and the c-axis lattice parameter should increase by ca. 0.5–1% to 0.5003–0.5027 nm [18,19]. The calculated c-axis values from XRD measurements for different pulse modes and radial positions are shown in Figure 4. As can be seen, the mostly unipolar pulse mode (Su = 90%) was almost homogenous along the whole radius. Film stress, as calculated with the wafer curvature method on a reference sample, i.e., an AlScN-coated 8 inch Si wafer without any electrode layers, was homogenous over the deposition area and around -700 MPa, therefore compressive. On the other hand, the pulse mode with a lower share of unipolar (Su = 60%) was more inhomogeneous, with a 2% bigger c axis in the wafer middle compared to the edge and thus a much higher compressive stress of above 1.5 GPa. This is in line with previous results, revealing higher plasma density near the substrate and higher energetic bombardment of the substrate at a higher share of bipolar pulse mode (see Figure 1, [14]).

with increasing in-plane compressive film stress. Additionally, besides the effect due to film stress, the lattice parameters a and c of AlScN increased with the incorporation of scandium into the wurtzite structure. The lattice parameters of AlN are a = 0.31114 nm

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**Figure 4.** Calculated c-lattice parameter of 0.9 µm films deposited with different hybrid pulse modes depending on radial position (PDF 25-1133; theoretical AlN lattice parameter c = 0.49792 nm, as well as calculated values for Al0.7Sc0.3N from [18,19] for comparison). **Figure 4.** Calculated c-lattice parameter of 0.9 µm films deposited with different hybrid pulse modes depending on radial position (PDF 25-1133; theoretical AlN lattice parameter c = 0.49792 nm, as well as calculated values for Al0.7Sc0.3N from [18,19] for comparison).

The rocking curves of (002) peaks shown in Figure 5 exhibited a similar behavior of radial dependencies. The films deposited at pulse mode Su = 90% had homogenous values of around 2.1–2.3° over the whole deposition range. In contrast to this, films deposited with a higher share of bipolar pulse mode showed a significant increase in FWHM from 1.5° in the middle, where energetic particle bombardment during film growth was highest, to 3° at the outer position, where energy bombardment was much lower. This is also in line with Figure 3, where the 2.5 µm-thick film deposited at pulse mode Su = 90% The rocking curves of (002) peaks shown in Figure 5 exhibited a similar behavior of radial dependencies. The films deposited at pulse mode S<sup>u</sup> = 90% had homogenous values of around 2.1–2.3◦ over the whole deposition range. In contrast to this, films deposited with a higher share of bipolar pulse mode showed a significant increase in FWHM from 1.5◦ in the middle, where energetic particle bombardment during film growth was highest, to 3◦ at the outer position, where energy bombardment was much lower. This is also in line with Figure 3, where the 2.5 µm-thick film deposited at pulse mode S<sup>u</sup> = 90% showed a homogenous occurrence of, although barely visible, (102) and (103) peaks, whereas the film deposited at pulse mode S<sup>u</sup> = 60% exhibited them only at the outermost position.

showed a homogenous occurrence of, although barely visible, (102) and (103) peaks, whereas the film deposited at pulse mode Su = 60% exhibited them only at the outermost

position.

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**Figure 5.** FWHM of (002) rocking curve of 2.5 µm films depending on radial position and pulse **Figure 5.** FWHM of (002) rocking curve of 2.5 µm films depending on radial position and pulse mode. take substrate deformation into account [16]. The bottom electrodes were 5 nm Ti and 40

#### mode. *3.2. Piezoelectric and Ferroelectric Properties* nm Pt, and the top electrodes were 100 nm Al with different electrode diameters from

*3.2. Piezoelectric and Ferroelectric Properties*  The piezoelectric properties were characterized on 1.5 mm-thick 4 inch Si wafers to take substrate deformation into account [16]. The bottom electrodes were 5 nm Ti and 40 The piezoelectric properties were characterized on 1.5 mm-thick 4 inch Si wafers to take substrate deformation into account [16]. The bottom electrodes were 5 nm Ti and 40 nm Pt, and the top electrodes were 100 nm Al with different electrode diameters from Ø0.5 mm to Ø2 mm for calculation of d33,f to take pad size effect into account. Ø0.5 mm to Ø2 mm for calculation of d33,f to take pad size effect into account. The material parameter d33,f of 0.9µm AlScN films is shown in Figure 6. Every data point refers to a least 20 single electrodes. These electrodes are within < ±5 mm distance to the noted radial position in the figure. As can be seen, the films deposited at a more

nm Pt, and the top electrodes were 100 nm Al with different electrode diameters from Ø0.5 mm to Ø2 mm for calculation of d33,f to take pad size effect into account. The material parameter d33,f of 0.9µm AlScN films is shown in Figure 6. Every data point refers to a least 20 single electrodes. These electrodes are within < ±5 mm distance to the noted radial position in the figure. As can be seen, the films deposited at a more unipolar pulse mode Su = 90% showed a homogeneous radial distribution of around 11– 12 pm/V with only a slight increase towards the outer coating area. This conforms with the XRD data, which show homogenous rocking curve FWHM. On the other hand, the more bipolar pulse mode resulted in films, which showed a maximum of d33,f = 10 pm/V in the middle of the deposition area and a decreasing value until reaching 7 pm/V at radial position around ca. 70 mm from the center with a slight increase towards higher radial positions again. The maximum value of d33,f was lower compared to films grown at higher The material parameter d33,f of 0.9µm AlScN films is shown in Figure 6. Every data point refers to a least 20 single electrodes. These electrodes are within < ±5 mm distance to the noted radial position in the figure. As can be seen, the films deposited at a more unipolar pulse mode S<sup>u</sup> = 90% showed a homogeneous radial distribution of around 11–12 pm/V with only a slight increase towards the outer coating area. This conforms with the XRD data, which show homogenous rocking curve FWHM. On the other hand, the more bipolar pulse mode resulted in films, which showed a maximum of d33,f = 10 pm/V in the middle of the deposition area and a decreasing value until reaching 7 pm/V at radial position around ca. 70 mm from the center with a slight increase towards higher radial positions again. The maximum value of d33,f was lower compared to films grown at higher unipolar pulse mode. This is somewhat congruent with the XRD data, as it shows an increase in FWHM of (002) rocking curve towards the edge, although FWHM started at a lower value compared to films deposited with a more unipolar pulse mode. unipolar pulse mode Su = 90% showed a homogeneous radial distribution of around 11– 12 pm/V with only a slight increase towards the outer coating area. This conforms with the XRD data, which show homogenous rocking curve FWHM. On the other hand, the more bipolar pulse mode resulted in films, which showed a maximum of d33,f = 10 pm/V in the middle of the deposition area and a decreasing value until reaching 7 pm/V at radial position around ca. 70 mm from the center with a slight increase towards higher radial positions again. The maximum value of d33,f was lower compared to films grown at higher unipolar pulse mode. This is somewhat congruent with the XRD data, as it shows an increase in FWHM of (002) rocking curve towards the edge, although FWHM started at a lower value compared to films deposited with a more unipolar pulse mode.

**Figure 6.** Dependency of d33,f of 1 µm AlScN films on radial position and share of unipolar pulse mode Su. **Figure 6.** Dependency of d33,f of 1 µm AlScN films on radial position and share of unipolar pulse mode Su.

mode Su.

Figure 7 shows the piezoresponse force microscopy measurements of AlScN deposited with pulse mode S<sup>u</sup> = 60% at two radial positions. The film surface at the inner radial position of 25 mm was homogenous with an arithmetic average roughness Ra of 1.4 nm, whereas the films at outer position of 100 nm showed a high density of abnormal-oriented grains (AOG) and thus a much higher roughness Ra of 9.7 nm. The measured piezoelectric amplitude showed the same behavior, being homogenous in the inner 25 mm position and having many areas without any piezoelectric activity at the 100 mm edge position of the deposition area. Additionally, the piezoelectric phase of films was unipolar (N-polar) at the inner position and bipolar at the outer position, meaning the film had grown both Aland N-polar. The cause for this is still under investigation. The most probable cause may be some local distortions during film growth, supported by the higher ratio of AOG on the surface. Figure 7 shows the piezoresponse force microscopy measurements of AlScN deposited with pulse mode Su = 60% at two radial positions. The film surface at the inner radial position of 25 mm was homogenous with an arithmetic average roughness Ra of 1.4 nm, whereas the films at outer position of 100 nm showed a high density of abnormal-oriented grains (AOG) and thus a much higher roughness Ra of 9.7 nm. The measured piezoelectric amplitude showed the same behavior, being homogenous in the inner 25 mm position and having many areas without any piezoelectric activity at the 100 mm edge position of the deposition area. Additionally, the piezoelectric phase of films was unipolar (N-polar) at the inner position and bipolar at the outer position, meaning the film had grown both Al- and N-polar. The cause for this is still under investigation. The most probable cause may be some local distortions during film growth, supported by the higher ratio of AOG on the surface.

**Figure 7.** PFM results (area 5 µm × 5 µm) of 2.5 µm AlScN, deposited with Su = 60% pulse mode, at radial positions 25 mm (**a**–**c**) and 100 mm (**d**–**f**): topography (**a**,**d**), piezoelectric amplitude (**b**,**e**) and piezoelectric phase (**c**,**f**). **Figure 7.** PFM results (area 5 µm × 5 µm) of 2.5 µm AlScN, deposited with S<sup>u</sup> = 60% pulse mode, at radial positions 25 mm (**a**–**c**) and 100 mm (**d**–**f**): topography (**a**,**d**), piezoelectric amplitude (**b**,**e**) and piezoelectric phase (**c**,**f**).

The ferroelectric switching of AlScN films deposited with pulse mode Su = 60% and 90% are exemplarily shown in Figure 8 for Ø0.75 mm top electrodes (area of 0.44 mm²). The polarization after switching was ca. 80 µC/cm² on the positive axis for both pulse modes. On the negative axis of applied electrical field, the polarization was 120 µC/cm² for Su = 60% and around 80 µC/cm² with higher leakage current for Su = 90% at negative electrical field. The coercive fields were at ca. 3.1 MV/cm and −3.5 MV/cm for Su = 60% and ca. 3 MV/cm and −3.3 MV/cm for Su = 90%, respectively. This is in line with the values reported by Fichtner et al., where AlScN with 27 at.% or 32 at.% Sc was reported to have a polarization of above 100 µC/cm² with coercive fields of around 4 to 5 MV/cm or 3 to 4 MV/cm, depending on the sign of electrical field, residual stress and Sc concentration [9]. Furthermore, Giribaldi et al. reported an effect of the electrode material on the Pt-AlScN-Al layer stack [20], a layout similar to this paper. They reported the effect of asymmetry of electrical properties as resulting from the combination of a Schottky junction at the Pt– AlScN interface and an ohmic contact at the AlScN–Al interface. As an additional factor, since the film stress of our sample was highly compressive, the resulting P-E loop and strain response on the applied electrical field shifted accordingly. Maximum strain at ±4 MV/cm for Su = 60% and 90% was 0.25% and 0.35% at positive strain (elongation of c axis) and 0.13%/0.18% and 0.23%/0.29% at negative strain (compression of c axis), respectively. This is in line with the higher piezoelectric activity (Figure 6) and better crystalline quality (Figure 3). The ferroelectric switching of AlScN films deposited with pulse mode S<sup>u</sup> = 60% and 90% are exemplarily shown in Figure 8 for Ø0.75 mm top electrodes (area of 0.44 mm<sup>2</sup> ). The polarization after switching was ca. 80 µC/cm<sup>2</sup> on the positive axis for both pulse modes. On the negative axis of applied electrical field, the polarization was 120 µC/cm<sup>2</sup> for S<sup>u</sup> = 60% and around 80 µC/cm<sup>2</sup> with higher leakage current for S<sup>u</sup> = 90% at negative electrical field. The coercive fields were at ca. 3.1 MV/cm and −3.5 MV/cm for S<sup>u</sup> = 60% and ca. 3 MV/cm and −3.3 MV/cm for S<sup>u</sup> = 90%, respectively. This is in line with the values reported by Fichtner et al., where AlScN with 27 at.% or 32 at.% Sc was reported to have a polarization of above 100 µC/cm<sup>2</sup> with coercive fields of around 4 to 5 MV/cm or 3 to 4 MV/cm, depending on the sign of electrical field, residual stress and Sc concentration [9]. Furthermore, Giribaldi et al. reported an effect of the electrode material on the Pt-AlScN-Al layer stack [20], a layout similar to this paper. They reported the effect of asymmetry of electrical properties as resulting from the combination of a Schottky junction at the Pt–AlScN interface and an ohmic contact at the AlScN–Al interface. As an additional factor, since the film stress of our sample was highly compressive, the resulting P-E loop and strain response on the applied electrical field shifted accordingly. Maximum strain at ±4 MV/cm for S<sup>u</sup> = 60% and 90% was 0.25% and 0.35% at positive strain (elongation of c axis) and 0.13%/0.18% and 0.23%/0.29% at negative strain (compression of c axis), respectively. This is in line with the higher piezoelectric activity (Figure 6) and better crystalline quality (Figure 3).

 **Figure 8.** DBLI measurement of polarization and strain of 1µm Al0.695Sc0.295N deposited with pulse **Figure 8.** DBLI measurement of polarization and strain of 1µm Al0.695Sc0.295N deposited with pulse mode S<sup>u</sup> = 60% (**left**) and S<sup>u</sup> = 90% (**right**) on Ti/Pt seed layer with Ø0.75 mm Al top electrode (= 0.44 mm<sup>2</sup> ) depending on electrical field, measured at 1 kHz, average of 100 measurements.

#### mode Su = 60% (**left**) and Su = 90% (**right**) on Ti/Pt seed layer with Ø0.75 mm Al top electrode (= 0.44 **4. Conclusions**

mode.

mm²) depending on electrical field, measured at 1 kHz, average of 100 measurements. **4. Conclusions**  This paper reports the deposition and characterization of ferroelectric AlScN films with a Sc content of 30 at.%. Film composition was largely homogenous at 29.5 ± 0.5 at.% Sc, with a decrease to 28 at.% at the edge due to geometric effects.

This paper reports the deposition and characterization of ferroelectric AlScN films with a Sc content of 30 at.%. Film composition was largely homogenous at 29.5 ± 0.5 at.% Sc, with a decrease to 28 at.% at the edge due to geometric effects. XRD θ–2θ scans revealed a highly oriented structure with high c-axis (002) orientation at all parameters, although thick films with a large share of unipolar pulse mode (Su = 90%) exhibited a small occurrence of (102) and (103) orientations with peak intensities of 1/3500th of (002) peak intensity. Calculation of c-lattice parameters revealed a homogenous distribution for more unipolar process conditions, with more bipolar pulse modes (Su = 60%) resulting in films with a higher c axis, i.e., more compressive stress, at the inner XRD θ–2θ scans revealed a highly oriented structure with high c-axis (002) orientation at all parameters, although thick films with a large share of unipolar pulse mode (S<sup>u</sup> = 90%) exhibited a small occurrence of (102) and (103) orientations with peak intensities of 1/3500th of (002) peak intensity. Calculation of c-lattice parameters revealed a homogenous distribution for more unipolar process conditions, with more bipolar pulse modes (S<sup>u</sup> = 60%) resulting in films with a higher c axis, i.e., more compressive stress, at the inner coating area. This is in line with known plasma parameter measurements, meaning higher plasma density in the center for bipolar process conditions. Rocking curve measurements of AlScN (002) peaks confirm this, as they revealed homogenous distribution of FWHM values for the 90% share of unipolar pulse mode of around 2.2 ± 0.1◦ and a radial distribution for the 60% share of unipolar pulse mode, with 1.5◦ at the center of the deposition area and 3◦ at the edge.

coating area. This is in line with known plasma parameter measurements, meaning higher plasma density in the center for bipolar process conditions. Rocking curve measurements of AlScN (002) peaks confirm this, as they revealed homogenous distribution of FWHM values for the 90% share of unipolar pulse mode of around 2.2 ± 0.1° and a radial distri-Piezoelectric characterization by double-beam laser interferometry showed d33,f values of 11–12 pm/V for films deposited by hybrid pulse mode S<sup>u</sup> = 90% process conditions and 10–7 pm/V for S<sup>u</sup> = 60% process conditions with a decrease towards outer coating areas. PFM measurements attribute the overall lower piezoelectric behavior of the films deposited by S<sup>u</sup> = 60% to a stronger occurrence of AOG and a bipolar phase distribution.

bution for the 60% share of unipolar pulse mode, with 1.5° at the center of the deposition area and 3° at the edge. Piezoelectric characterization by double-beam laser interferometry showed d33,f val-The films showed ferroelectric switching behavior with coercive fields of 3 MV/cm to 3.5 MV/cm for 0.9 µm AlScN films. Polarization of the films reached 80–120 µC/cm<sup>2</sup> , depending on switching direction and pulse mode. The maximum strain at the highest field of 4 MV/cm was around 0.35%, also depending on switching direction and pulse mode.

ues of 11–12 pm/V for films deposited by hybrid pulse mode Su = 90% process conditions and 10–7 pm/V for Su = 60% process conditions with a decrease towards outer coating areas. PFM measurements attribute the overall lower piezoelectric behavior of the films deposited by Su = 60% to a stronger occurrence of AOG and a bipolar phase distribution. In short, the influence of pulse powering variation by special unipolar–bipolar hybrid pulse mode on resulting film properties of AlScN was investigated. It was shown that good structural and piezoelectric properties can be achieved with very high deposition rates of up to 200 nm/min on large areas using this hybrid pulse mode operation.

The films showed ferroelectric switching behavior with coercive fields of 3 MV/cm to 3.5 MV/cm for 0.9 µm AlScN films. Polarization of the films reached 80–120 µC/cm², depending on switching direction and pulse mode. The maximum strain at the highest field of 4 MV/cm was around 0.35%, also depending on switching direction and pulse **Author Contributions:** Conceptualization, S.B. and H.B.; Formal analysis, S.B., S.C., O.Z. and T.M.; Funding acquisition, S.B. and H.B.; Investigation, S.B., T.S., O.Z. and T.M.; Methodology, S.B. and S.C.; Project administration, S.B. and H.B.; Supervision, S.B. and H.B.; Writing—original draft, S.B.; Writing—review and editing, S.B., T.S., S.C., O.Z., T.M. and H.B. All authors have read and agreed to the published version of the manuscript.

rates of up to 200 nm/min on large areas using this hybrid pulse mode operation.

In short, the influence of pulse powering variation by special unipolar–bipolar hybrid

pulse mode on resulting film properties of AlScN was investigated. It was shown that

**Author Contributions:** Conceptualization, S.B. and H.B.; Formal analysis, S.B., S.C., O.Z. and T.M.; Funding acquisition, S.B. and H.B.; Investigation, S.B., T.S., O.Z. and T.M.; Methodology, S.B. and S.C.; Project administration, S.B. and H.B.; Supervision, S.B. and H.B.; Writing—original draft, S.B.; Writing—review and editing, S.B., T.S., S.C., O.Z., T.M. and H.B. All authors have read and agreed

to the published version of the manuscript.

**Funding:** This research was partly funded by the ECSEL Joint Undertaking (JU), for the project "Pilot Integration 3nm Semiconductor technology (Pin3S)", grant number 826422. The JU receives support from the European Union's Horizon 2020 research and innovation program and Netherlands, Belgium, Germany, France, Romania and Israel. This research was also partly funded under the project "Tragbare, Autarke und Kompakte Strom Generatoren (TASG)" by the European Regional Development Fund (ERDF) and the Free State of Saxony under grant number 100347675.

**Data Availability Statement:** The data presented in this study are available on reasonable request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript or in the decision to publish the results.
