Application of a novel contactless conductivity sensor in chemical vapor deposition of aluminum films

A novel contactless method for conductivity sensing is introduced that utilizes a driving coil and two tunable and near resonant coils. The design uses only inexpensive electronic components and a variable frequency rf generator. An algebraic expression for the response has been derived and simulations indicate a linear response to surface conductivity changes over at least four orders of magnitude. The sensitivity is shown to depend on the conductivity of the substrate, with a limit to conductivity changes as low as 10(-4) Omega(-1) for insulating substrates. An ultrahigh vacuum compatible version of this probe has been used to monitor in situ aluminum thin film growth by chemical vapor deposition on a native oxide covered, highly doped, Si(lll) wafer. On this semiconducting substrate (3 Omega(-1)) a sensitivity to sheet conductivity changes as low as similar to 2 x 10(-2) Omega(-1) has been demonstrated. The Al films show a discrete jump in differential sheet conductivity associated with Al cluster coalescence during growth. (C) 1997 American Institute of Physics.