การเตรียมฟิล์มบางโมลิบดีนัมที่มีความเค้นตกค้างต่ำโดยดีซีแมกนิตรอนสปัตเตอริง / เฉลิมวัฒน์ วงศ์วาณิชวัฒนา = Preparation of low residual stress molybdenum thin films by DC magnetron sputtering / Chalermwat Wongwanitwattana
Molybdenum (Mo) thin films deposited on soda-lime glass by dc magnetron sputtering are normally used as back contact for copper-indium-gallium-diselenide (CIGS) thin film solar cells. The appropriate properties of Mo thin films to be used for the device are films with low resistivity, and highly adhere to the glass substrate. In addition, the films must be highly tolerate to the change of temperature. These properties can be managed by controlling the argon (Ar) pressure during the deposition process. For Mo films sputtered by using low Ar pressure, the resistivity is low, but the residual stress is high and poor in adhesion. In the contrary, for films sputtered by using high Ar pressure, the resistivity is high together with low residual stress and good adhesion. From this experiment, for monolayer films of 2,500 Å, sputtered at 4x10[superscript -3] mbar, the resistivity is in the range of 2.12x10[superscript -5] omega cm. The residual stress of films is high, resulting in the low adhesion which has the value of 1765 kPa as determined by the pull-off technique. For Mo films sputtered at 8x10[superscript -3] mbar, the resistivity is in the range of 11.06x10[superscript -5] omega cm. These films are low in residual stress and highly adhere to the soda-lime glass. Thus, in order to compensate the resistivity and adhesion, bilayer films are developed. Mo bilayer films which are deposited at 8x10[superscript -3] mbar follow by 4x10[superscript -3] mbar with the total thickness of 2,500 Å has high adhesion of 2971 kPa together with moderate resistivity of 4.48x10[superscript -5] omega cm. In conclusion, the appropriate Mo films to be used as the back contact for CIGS thin film solar cells are monolayer films sputtered at Ar pressure of 5x10[superscript -3] mbar. The average resistivity of these films are 2.53x10[superscript -5] omega cm, together with low residual stress and moderate adhesion of 2337 kPa.
