Browsing by Author "WANG, SW"

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A SIMPLE AND EFFICIENT PRETREATMENT TECHNOLOGY FOR SELECTIVE TUNGSTEN DEPOSITION IN LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION REACTOR
(1994-12-01)
CHANG, KM
;
YEH, TH
;
LI, CH
;
WANG, SW
;
電子工程學系及電子研究所
In this paper rye develop a two-step pretreatment method which is a simple but effective cleaning process that can be used to achieve a high deposition rate and excellent interface characteristics, as well as improve the selectivity. In the first step, we use CF4/O-2 mixing gases as a plasma etching system without substrate bias. The removal of damage and contaminants by reactive ion etching (RIE) during contact hole opening can thus be obtained. We consider that the role of oxygen is first to oxidize the polymer residues (i.e., fluorocarbons like CxFy) and the RIE-damaged regions on the silicon surface, and it is then followed with CF4 to remove these oxides. experiments, the plasma modification rate can be controlled at 120 Angstrom/min. Results of the high deposition rate, smooth interface, low selectivity loss and the other improvements are observed. These are superior to those of cases without pretreatment. The second step is that anhydrous HF cleaning was used to remove surface oxide which was formed during the first step. Obviously, this new cleaning technology is very efficient not only for contact hole pretreatment but also for polysilicon materials. This also implies that this technology may have potential for polycide gate applications.
ACTIVITY-COEFFICIENTS OF ELECTRONS AND HOLES IN DEGENERATE SEMICONDUCTORS WITH NONUNIFORM COMPOSITION
(1994-03-01)
CHANG, KM
;
YEH, TH
;
WANG, SW
;
LEE, CH
;
電子工程學系及電子研究所
A new simple, general and rigorous analytic expression for the equilibrium activity coefficients of electrons and holes in degenerate semiconductors with nonuniform composition is presented. These activity coefficients are functions of the carrier degeneracy (Fermi-Dirac statistics), the band gap, the electron affinity and the density of states which vary with position. The calculation of carrier activity coefficients requires the selection of chemical potential and electrostatic potential references. The choice of these reference states is addressed. The relationships between purely thermodynamic quantities and parameters of the band theory are also presented. Emphasis is also placed on formulating an equation in a simple, Boltzmann-like form in which the nonideal behavior is described by two parameters, the effective band-gap shrinkage, DELTAE(g), and the effective asymmetry factor, A. In this form the working equations for the carrier densities and activity coefficients are convenient for use in computer-aided analysis and design. The approach presented here allows convenient treatment of nonuniform degenerate semiconductors in a manner that is consistent with thermodynamics as well as with the Poisson-Boltzmann equation for the electrostatic potential.