= 0+1866XLO 1) a) A bare Si wafer is oxidized in dry O2 at 1100 °C. The desired final thickness is 50 nm. J i) Find the time required to perform

the oxidation, ignoring rapid growth. ii) Find the time required to perform the oxidation, taking rapid growth into account. tox Use Deal-Grove equations - do NOT use oxide growth curves. b) A <111> silicon wafer is oxidised using the following sequence i) 60 mins @ 1000°C in dry O₂. ATB 0,065 [10 1/3 marks] ii) 60 mins @ 1000°C in steam. 0.125 iii) Locally etch 0.1 microns of oxide to create a trench. iv) 30 mins @ 1100°C in dry O2. 0.009 Use growth curves to calculate the oxide thickness after each step. [10 marks c) It is possible to determine the thickness of oxide on oxidised wafers by visual inspection. Describe the method and discuss TWO disadvantages of this technique. [5 marks] d) Discuss FIVE of the features of SiO₂ which account for its widespread use in microelectronics. Breack down $h field [5 marks e) Dry oxidation is much slower than wet oxidation. Discuss briefly any advantages to using dry oxides instead of wet oxides. [3 mark -Excellent stable Passivation Excellent and stable Eelectricat Properties If the wet wild is s is day,