Growth Kinetics Of SiO 2 On (001)Si Catalyzed By Cu 3 Si At Elevated Temperatures
- PDF / 1,915,236 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 105 Downloads / 249 Views
ABSTRACT The oxidation of Si catalyzed by 170-nm-thick Cu 3Si at elevated temperatures has been investigated by transmission electron microscopy and Auger electron spectroscopy. For wet oxidation at 140-180 -C, the growth rate of the oxide layer was increased with the temperature. On the other hand, as the temperature was increased above 200 C, the growth rate slowed down. The growth kinetics of oxide was investigated. Controlling mechanisms for the growth of oxide owing to the grain growth of Cu 3Si are discussed. The activation energy for the linear growth of oxide was measured to be 0. 19 + 0.1 eV. INTRODUCTION As the device size steadily scales down, the packing density is increasing. Interconnection lines increase in length and reduce in feature size. Reduction in interconnect pitch increases wiring resistance and parasitic capacitance. These conditions result in an increase in RC delay time and crosstalk noise. To satisfy the demands for ULSI fabrication, it is necessary to look for a new material to replace Al and its alloys. Cu is an attractive material for interconnects due to its low bulk resistivity and high resistance to electromigration [1]. Very peculiar oxidation behaviors on both (001)Si and (11 1)Si catalyzed by Cu3Si were found [2-4]. Mechanisms of fast oxidation on Si substrate at room temperature (RT) are now largely understood. For copper films deposited on Si substrates, 11"-Cu3Si layer was formed on top of Si substrate after annealing in the temperature range of 200-700 "C [5]. Once the Cu 3Si layer is formed, oxidation occurs at the grain boundaries of Cu 3 Si first [4]. Oxygen reacts with Cu 3Si to form Si0 2 and Cu according to the relationship: Cu 3 Si + 20 -- Si0 2 + 3Cu. The copper atoms are released by oxidation of Cu 3Si, and move readily to the Si substrate to form new Cu 3Si according to the relationship: 3Cu + Si -- Cu 3Si. As long as the oxidants were supplied to the buried interface, the sequence may continue catalytically, to form a thick Si0 2 layer [2]. On the other hand, some of the released copper atoms do not participate in the reconstruction of Cu 3Si. Instead, these Cu atoms agglomerate to form Cu precipitates. As a result, the oxidation process terminates if Cu atoms are totally deprived from the Cu 3 Si at the buried Si0 2 /Si interface [3]. The oxidation behaviors at relatively high temperatures, compared with that at room temperature, are still not well understood. The present study concentrated on the investigation of oxidation behaviors of Cu 3Si on silicon at elevated temperatures. The growth kinetics of oxide were investigated. Controlling mechanisms for the growth of oxide are discussed. EXPERIMENTAL PROCEDURES Single crystal, 3-8 fl-cm, 2 inches in diameter n-type (001) oriented silicon wafers were 217 Mat. Res. Soc. Symp. Proc. Vol. 564 © 1999 Materials Research Society
used in the present study. The wafers were first cleaned by a standard procedure followed by dipping in a dilute HF solution (HF : H20 = 1 : 50) immediately before loading into an ultrahigh va
Data Loading...
