Characterization of high-K dielectric ZrO2 films annealed by rapid thermalprocessing

In this investigation, two kinds of ZrO2 samples were prepared. The ZrO2 fi lms of about 150 Angstrom by PVD were used for physical characterization an d the ultrathin ZrO2 films of about 40 Angstrom by RTCVD were used for elec trical characterization of MOS capacitors. The samples were annealed in a r apid thermal processing (RTP) system at temperatures of 400-1050 degreesC i n various gas ambients, including O-2, N-2, forming gas (H-2/Ar), wet H-2 ( 15% H2O in H-2), and wet O-2 (15% H2O in O-2). Spectroscopic ellipsometry ( SE) with a two layer BEMA optical model was used to characterize the ZrO2 t hickness and evaluate the microstructure. A wet etch rate test of ZrO2 film s in 1:100 HF solution using SE indicated two distinct etch rates, with a s lower initial rate followed by a faster rate. The measured etch rates are d ependent of temperature, indicating 4.85 and 38.9 Angstrom /min at 25 and 4 5 degreesC, respectively. The RTP annealing temperature and gas ambients ha ve a significant effect on the ZrO2 film etch rate. Rutherford backscatteri ng spectrometry (RBS) and x-ray photoelectron spectroscopy depth profile we re used to characterize the films. Three ZrO2 samples were measured by both cross section transmission electron microscopy and SE, indicating that the thickness difference between two techniques is only 1 A. A mercury probe w as used to characterize the electrical properties of the physical vapor dep osition dielectric films. The electrical characterization of ultrathin ZrO2 films show that the gas ambients in postdeposition anneal affect the equiv alent oxide thickness (EOT) and leakage current significantly. The lowest E OT achieved in this study is 10.9 Angstrom for the sample spike annealed in N-2. The RTP effect on electrical properties of ultrathin ZrO2 was also di scussed. (C) 2001 American Vacuum Society.