Growth, Structure and Stress of DC Magnetron Sputtered TiB 2 Thin Films
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for protective coatings, and these properties are primarily influenced by sputtering process parameters such as deposition power and pressure as well as film thickness. Therefore, the relationships among the film microstructure, residual stress and deposition parameters should be a primary concern in our research. As reported in previous work[6], the microstructure and residual stress of TiB 2 thin films deposited using magnetron sputtering depends on the film thickness. In this continuing investigation, we focused on the examination of the effects of the deposition power and pressure on the microstructure and residual stress of TiB 2 thin films. In the sputtering process, a series of combinations of deposition power and total Ar pressures was used. The microstructure of as-deposited films was examined by X-ray diffraction. It was observed that the microstructure is highly sensitive to deposition conditions. Depending on the sputtering power and pressure, two types of crystalline structure are observed: a randomly oriented fine crystalline structure and a coarser grained (001) textured structure. The results of residual stress measurement by a wafer curvature technique indicate a stress transition from compression to tension as the Ar pressure increases for as-deposited films at all the powers investigated and a transition from tensile to compressive in a certain pressure range when the deposition power increases. EXPERIMENTAL PROCEDURE Deposition of TiB2 Films was carried out in a Vac-Tec Model 250 Batch Side Sputtering System using dc magnetron sputtering. The sputtering target used is a 99.5% TiB 2 disk with a 4" diameter. Wafers are 2 diameter oxidized silicon (111), 7059 Coming glass and carbon coated 181
Mat. Res. Soc. Symp. Proc. Vol. 356 01995 Materials Research Society
copper grids. Three dc power levels: 100, 400, 600 W, and four Ar pressures: 3, 5, 8, and 12 mTorr were used during the sputtering process in order to examine the effects of these parameters on the structures and the stresses of the deposited films. The deposition rate was in the range of 63 to 465 /min under the above sputtering conditions. For the purpose of controlling the total thickness of the films in a proper range when the deposition powers used were very different, deposition time was set for 25, 12 and 8 minutes for the corresponding deposition powers of 100, 400 and 600 W, respectively. However, because the deposition rate at 100 W was too low, the total thickness (about 1800 A) of the films deposited under this power was still less than that of the films with the other two powers (3000 - 4000 A). Nevertheless, the deposition rates obtained under different conditions were consistent, as can be seen in Figure 1 below. The characterization of the deposited films was carried out to determine crystal structure and residual stresses. The structures of the deposited films were investigated with a Rigaku D/Max-2BX X-ray Diffractometer with Cu Ka radiation using a thin film goniometer. The methods used in X-ray scanning are the same as
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