Effect of AC target power on AlN film quality

Abstract

The influence of alternating current (AC) target power on film stress, roughness, and x-ray diffraction rocking curve full width half maximum (FWHM) was examined for AlN films deposited using S-gun magnetron sputtering on insulative substrates consisting of Si wafers with 575 nm thermal oxide. As the AC target power was increased from 5 to 8 kW, the deposition rate increased from 9.3 to 15.9 A/s, film stress decreased from 81 to −170 MPa, and the rocking curve FWHM increased from 0.98 to 1.03°. AlN film behavior is observed to change with target life; films deposited at 200 kWh target life were approximately 40 MPa more compressive and had 0.02° degree higher rocking curve FWHM values than films deposited at 130 kWh. AlN films deposited in two depositions were compared with films deposited in a single deposition, in order to better characterize the growth behavior and properties of AlN films deposited on an existing AlN film, which is not well understood. Two deposition films, when compared with single deposition films, showed no variation in residual stress trends or grain size behavior, but the average film roughness increased from 0.7 to 1.4 nm and rocking curve FWHM values increased by more than 0.25°.

Highly c-axis oriented AlN film grown by unbalanced magnetron reactive sputtering and its electrical properties

“…When the coil current increases from 0 to 1.0 A, it is obvious that the intensity of the AlN (002) peak increases, and the intensity of the AlN (100) peak decreases. This phenomenon was also observed in AlN films grown by magnetron sputtering with substrate heating or with increasing sputtering power [22][23][24][25]. The AlN-1.0 has a stronger and sharper (002) AlN peak, indicating that this AlN film is highly c-axis oriented.…”

“…Another benefit of the additional magnetic field is that it could increase the energy of the deposited particles, like the effect of increasing temperature of the substrate or the sputtering power [23][24][25], both being conducive to the formation of highly c-axis oriented AlN films. This can be explained as follows.…”

Reduction of residual stress in AlN thin films synthesized by magnetron sputtering technique

“…Tensile to compressive 6 -6.5 kW RF reactive sputtering [25] Compressive to Tensile 3.99 -5.32×10 −3 mbar pulsed DC sputtering [26] Compressive to tensile 6.6 -13.3 × 10 −3 mbar RF reactive sputtering [27] Compressive to tensile 6 -8 × 10 −3 mbar DC reactive sputtering [13] Table 3. Residual stress of AlN films at different sputtering power and pressure.…”

Ultraminiature AlN diaphragm acoustic transducer

“…The addition of residual stress modifies the governing equations for the system as given in Timoshenko and Woinowsky-Krieger. 14 For instance, if there is 50 MPa of tensile stress in the piezoelectric layer of the diaphragm (possible with different types of film deposition 12,15 ) the MDP will be 2.5 dB higher than the no-stress case (using 18% electrode coverage). The optimal electrode coverage for 50 MPa residual stress is 16%, which only provides about 1% MDP improvement over 18% coverage.…”

“…Although it is impossible to completely eliminate residual stress in the AlN, lower residual stress is possible. 15 The blue "Ã" represents the predicted MDP for a 9.6 Â 10 -8 m 2 area sensor with low stress (50 MPa) and high-quality piezoelectric film (d 31 ¼ À2:51 pm/V and tan d ¼ 0.002). 17 Consistent with the red lines above, the blue dashed and dotted lines that intersect this point in Fig.…”