Shuzo Sano

High-speed Forming of Low-resistivity Interconnects Using Laser-induced CVD.

Experimental investigations concerning formation of metal interconnects on LSI chips using laser-induced CVD are described. Molybdenum conductors were deposited by pyrolytic decomposition of molybdenum hexacarbonyl using argon ion-laser irradiation. Increasing molybdenum hexacarbonyl pressure, increasing laser power and decreasing writing speed were accompanied by increasing width and thickness of molybdenum conductors. Decomposition efficiency is 20 to 30% which is higher than conventional thermal CVD. Increased width and thickness diminished the resistance of the conductors, but the resistivity was almost independent of the forming conditions and higher than that of bulk molybdenum. Auger electron spectroscopy revealed that the high resistivity of the as-deposited films was due to the presence of carbon and oxygen as impurities. These impurities are removable by laser annealing in a vacuum, whereby the resistivity can be reduced to 10 μΩ·cm. These low-resistivity conductors can be applied to fault analysis or repair of not only MOS devices but also linear and bipolar devices.

Reduction of Contact Resistance in Interconnections Formed by Laser-Induced CVD.

Reduction of Contact Resistance in Interconnections Formed by Laser-Induced CVD Mikio HONGO, Takashi KAMIMURA, Shuzo SANO and Katsuro MIZUKOSHI This paper reports the experimental results of the reduction in contact resistance between aluminum conductors in a semiconductor device and molybdenum conductors deposited by laser-induced CVD. The contact holes are formed by focused ion beam through a passivation layer on the chip surface, and irradiated with an argon ion laser in a molybdenum-hexacarbonyl atmosphere. The holes can be filled with molybdenum, however, aluminummolybdenum contact resistance is very high. Even after sufficient removal of natural oxide, the contact resistivity with the molybdenum line formed cross on the aluminum line without a passivation layer is high. The high-resistive contact is caused by the formation of high-resistive alloy diffused aluminum into molybdenum. To prevent alloying, chrominum film was adopted as a barrier layer at the aluminum-molybdenum interface. As a result, the contact resistivity was reduced to 1/100. Automatic positioning using a pattern matching technique and an end-point monitor using a detection in change of the intensity of reflective light can realize low-resistive contact and good outward shape with good reappearance.