TEM imaging of thick, multi-layer AlN film deposited on oxide

High resolution TEM imaging was performed of a two layer 1.50 ± 0.09μm thick AlN film deposited using the Tegal AMS 2004 S-gun magnetron sputter system on 565nm of thermal oxide. The AlN film was deposited in two depositions, with vacuum broken in between. Process induced faults and dislocations are observed at both the AlN-substrate interface and at the film location where vacuum was broken, but irregularities are generally resolved within 5nm. Additional roughness and stacking faults are observed in the last 6nm of film deposition. Bright field imaging of the film shows a distinct line of discontinuity at the film location where vacuum was broken between depositions; however, the grain structure of the film remains largely continuous across the discontinuity. A film deposited under the same conditions as the measured sample, but deposited in one deposition, had comparable stress (<50 MPa), thickness, and grain size properties. Increased XRD rocking curve FWHM values for the two deposition film (1.29+/-0.01°) as compared with the single deposition film (0.97+/-0.01°) is likely due to the stacking irregularities introduced at the location where vacuum was broken.