Interval Annealing During Alternating Pulse Deposition
- PDF / 102,362 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 37 Downloads / 172 Views
D1.3.1
Interval Annealing During Alternating Pulse Deposition J.F. Conley, Jr., D.J. Tweet, Y. Ono, and G. Stecker IC Process Technology Laboratory, Sharp Labs of America, Camas, WA ABSTRACT Thin films deposited via atomic layer deposition at low temperature tend to be less dense than bulk material and typically require high temperature post deposition annealing for densification and removal of unreacted precursor ligands. We have found that improved film densification can be achieved by interval annealing, in which in-situ moderate temperature (~420°C) rapid thermal anneals are performed after every n deposition cycles. HfO2 film density and refractive index were found to increase with decreasing anneal interval (more frequent annealing). The highest density films could be achieved only by every-cycle annealing and could not be achieved by post deposition annealing. The densified every cycle annealed films have been shown to have improved equivalent thickness and leakage and decreased interfacial layer thickness.
INTRODUCTION Compared with other techniques, atomic layer deposition (ALD) offers many advantages such as excellent conformality and atomic scale control [1]. However, due to low process temperatures, thin films deposited via atomic layer deposition tend to be less dense than the bulk material. Densification, which may involve the removal of impurities such as C, Cl, N, etc. [28], typically requires high temperature post deposition annealing (PDA) that may violate the thermal budget of a sensitive process. We have found that film densification can be achieved by interval annealing, in which in-situ moderate temperature (~420°C) rapid thermal anneals are performed after every n deposition cycles. Film thickness and deposition rate / cycle were found to decrease and film density and refractive index were found to increase with decreasing anneal interval (more frequent annealing). Using interval annealing, we have been able to "tune" the density of HfO2 thin films from ~7.7 for samples annealed only at the end of the deposition to ~10 g/cm3 for samples annealed after every deposition cycle. It was found that the highest density films could be achieved only by every-cycle annealing. For thick films annealed every cycle, x-ray diffraction (XRD) reveals an additional crystallization peak suggesting the presence of a dense orthorhombic phase. The level of densification observed in the every cycle annealed films could not be achieved by post deposition annealing and was likely due to a more efficient intermediate removal of unreacted precursor ligands (with surface rearrangement) before they can become trapped by subsequent layers. Every cycle annealing of ALD HfO2 films was previously shown to result in a substantial improvement of electrical properties and a reduction in interfacial layer thickness [7,8].
EXPERIMENTAL DETAILS HfO2 films were deposited on 150 mm prime grade (100) Si substrates via a dual metal precursor technique [9,10] in which alternating pulses of Hf(NO3)4 and HfCl4 precursors are
D1.3.2
Data Loading...
