AVS 46th International Symposium
    Electronic Materials and Processing Division Tuesday Sessions
       Session EM-TuA

Invited Paper EM-TuA1
Challenges in Gate Dielectric Scaling

Tuesday, October 26, 1999, 2:00 pm, Room 608

Session: High Dielectric Constant Materials and Thin Oxides
Presenter: D.P. Monroe, Bell Labs, Lucent Technologies
Authors: D.P. Monroe, Bell Labs, Lucent Technologies
B.E. Weir, Bell Labs, Lucent Technologies
M.A. Alam, Bell Labs, Lucent Technologies
J. Bude, Bell Labs, Lucent Technologies
P.J Silverman, Bell Labs, Lucent Technologies
T. Sorsch, Bell Labs, Lucent Technologies
M.L. Green, Bell Labs, Lucent Technologies
A. Ghetti, Bell Labs, Lucent Technologies
Y. Ma, Bell Labs, Lucent Technologies
Y. Chen, Bell Labs, Lucent Technologies
F. Li, Bell Labs, Lucent Technologies
Correspondent: Click to Email
Extrapolation of current trends in CMOS suggest that the gate dielectric of 2010 will have a capacitance equivalent to <15Å of SiO@sub 2@, including the nonzero thickness of the charge sheets in gate and substrate. It must withstand penetration of elements such as Boron during processing, and of electrons and holes during operation. It must tolerate damage from highly energetic carriers excited by the voltages on gate and drain over a multi-year operating life. Proposed replacements for SiO@sub 2@ must also demonstrate materials compatibility with the Si substrate and the gate material (currently also Si). The successful candidate will have a fewer than one interface defect for 10,000 atoms, and a uniformity across wafers, lots, and runs of better than 10% (3@sigma@). We will discuss these daunting materials and processing challenges from a transistor and circuit perspective, concentrating on the capacitance, mobility, boron penetration, and time-dependent dielectric breakdown of SiO@sub 2@ and nitrided oxides thinner than 30Å, as measured by ellipsometry. The electrical thickness of such oxides is thicker by at least 5Å, depending strongly but reproducibly on the oxide field. Simple measurements of this dependence are critical to understanding the transistor drive capability and the leakage current. The breakdown properties are more strongly governed by the applied potentials than the field. However they are strongly sensitive to the polarity of the gate voltage, even after care has been taken to include the large effects of band bending. This indicates the important role of the carrier dynamics in the anode. The "soft" breakdown of these thin oxides indicates a reduced role of positive feedback that results in higly conductive filaments in thicker oxides; indeed, some transistors continue to function even after "breakdown." We will outline some ideas for the physical mechanisms underlying the special properties of breakdown in these films.