AVS 58th Annual International Symposium and Exhibition
    Advanced Surface Engineering Division Thursday Sessions
       Session SE+PS-ThA

Paper SE+PS-ThA7
Plasma Study and Interconnect Metallization using a Modulated Pulse Power (MPP) Hollow Cathode Magnetron

Thursday, November 3, 2011, 4:00 pm, Room 104

Session: Pulsed Plasmas in Surface Engineering
Presenter: Liang Meng, University of Illinois at Urbana Champaign
Authors: L. Meng, University of Illinois at Urbana Champaign
H. Yu, University of Illinois at Urbana Champaign
T.S. Cho, University of Illinois at Urbana Champaign
S. Jung, University of Illinois at Urbana Champaign
D.N. Ruzic, University of Illinois at Urbana Champaign
Correspondent: Click to Email
Modulated pulse power (MPP) magnetron sputtering, as a derivative of high power pulsed magnetron sputtering (HPPMS), was applied to a 200 mm hollow cathode magnetron (HCM) with a Cu target. The aim was to develop a more advanced ionized physical vapor deposition (IPVD) tool for applications such as interconnect metallization for sub-32 nm technologies. The MPP plasma generator, featured with 1000 V maximum pulse voltage and 550 A maximum pulse current, has a unique advantage of flexibly adjusting on- and off-time for each individual pulse, so that a long pulse packet of several milliseconds with desired waveform shapes can be generated. Distinct discharge stages were normally observed in one MPP pulse packet. Time-dependent plasma parameters were investigated using a triple Langmuir probe to help understand the MPP discharge characteristics and its performances. Plasma behaviors were shown to closely depend on the pulse waveforms and various other parameters including pulse current, repetition frequency, pressure, and distance from the target. A high electron density (ne) of 3×1018 m−3 and an electron temperature (Te) of 5 eV during the pulse were obtained at the substrate level, with an average power less than 8 kW. Compared with the DC magnetron sputtering at the same average power, the pulsed plasma density was an order of magnitude higher, which resulted in an enhanced ionization of the sputtered flux. As measured by an electrostatic gridded energy analyzer combined with a quartz crystal microbalance, the Cu ionization fractions above 30% were easily achieved by the MPP sputtering on the substrate level, twice higher than those by the DC sputtering. Increasing the pulse duty ratio or reducing the pressure resulted in a stronger ionization. The performance of Cu deposition in narrow trenches (70-100 nm) using the MPP sputtering was further studied, which exhibited an improvement over the DC sputtering. Stronger pulses with higher duty ratios and a lower gas pressure were preferred to reduce the overhang and achieve better step coverage and bottom coverage.