Improvement of oxide thickness determination on MOS structures using capacitance–voltage measurements at high frequencies

✍ Scribed by L. Soliman; E. Duval; M. Benzohra; E. Lheurette; K. Ketata; M. Ketata

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 111 KB
• Volume: 4
• Category: Article
• ISSN: 1369-8001
• DOI: 10.1016/s1369-8001(00)00131-1

✦ Synopsis

It is well known that capacitance-voltage (C2V) measurements provide a simple determination of oxide thickness, but with the scaling down of components the classical method is not appropriated any more. We have observed that for two devices with the same oxide thickness and different surfaces, the classical method is accurate for large area but it is not adapted for the small one. We present a new procedure to make an accurate electrical determination of the oxide thickness on metal-oxide-semiconductor (MOS) structures of low dimensions in U.L.S.I. technology. Our method does not require a measurement in strong accumulation. It is based on C2V measurements at frequencies higher than 1 MHz associated to a non-linear optimisation of the experimental and theoretical band bending versus bias voltage curve (C S ¼ f ðV g Þ), in the depletion mode. By this way, a corrective factor is estimated with precision in order to make an accurate determination of the oxide thickness value. We show that the frequency associated to the non-linear optimisation of C S ¼ f ðV g Þ is function of the MOS device dimensions and is increased when the surface decreases. The experimental results obtained on low-dimension MOS structures and different oxide thickness are precise and in total agreement with those measured by ellipsometry. By using our new procedure the accuracy of oxide thickness determination is improved.