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Unformatted text preview: N.CHEUNG,Sp 2008 EEC243: ADVANCED IC PROCESSING AND LAYOUT Homework #9 Solutions Problem 1 (a) d= 2.5 mm C = 1 pF/cm 2 J=1mA/cm 2 V=1000V From C= Q/V , Q = 10 -9 Coulombs/cm 2 J= Q/t , t = 10-6 sec (b) A typical RF frequency ( f =1/t) > 1 MHz can create a net surface charge transfer =0 at steady state . Problem 2 (i) Large loading effect will reduce the fluorine radicals in the plasma. This effectively reduces the F/C ratio and gives lower etching rate. (ii) SiO 2 is considered to be an oxygen source when etched. When oxygen is present in the gas mixture, the C concentration will be lowered. The effective F/C ratio will increase and the tendency for polymerization to occur is reduced. Another thoery (Coburn et al) states that CF x has a lower adsorption on SiO 2 than Si. Therefore, less polymerization also. (iii) Ion bombardment enhances the surface etching processes because it can sputter away surface passsivation layers. We will expect a lower selectivity ratio between two materials if ion bombardment passsivation layers....
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This note was uploaded on 11/02/2010 for the course EECS 243 taught by Professor Ee243 during the Spring '03 term at University of California, Berkeley.
- Spring '03