Question

1. Start with bare (111) silicon wafer. You want to grow 1 um of SiO2 using dry (for the first 500 Å) and wet oxidation at 1,000 °C. Calculate total time. 2. Local oxidation is a process that is widely used to provide lateral isolation between devices in IC chips. In some cases, it is desirable to end up with a more planar surface than standard LOCOS provides, and so a silicon etch is used prior to the oxidation step as illustrated in figure. For the structure with 0.5 um of silicon etched prior to the oxidation, how long must the wafer be oxidized at 1,000 °C in H2O to produce the planar oxide shown on the right? Si NE SO, LOCOS Oxide 0.5 um (100) Si (100 Si

Answer 1

B = Parabolic Rate, B₀ = Parabolic rate constant

B/A = Linear rate , (B/A)₀= Linear rate constant

x₀ = thickness of silicon oxide

T = absolute Temperature

E_a = Activation energy

Que Solation The Step is to find dhe linear first 6-3 at Lotoc Cardficint and Parabelic 1273 K (in abalude tempunotse -En/RT) Lineor rate 2 A LEnT) Bo BTO Perabolic Tate Parareter O Roantily Wet Linear rate O 16 6.23X 106 Contant O 2 0 Panats lic Rote 772 Cans dant 0i78 O 23 EA this find the Vae Consdant Linear Parabs bic rate andl date 2.0 &517 X 10X1273 e 6,23 X106 um 0.075 i4 AA

Parabo lic Rate Ar dy 8.617 X10-1 2 ? 3 772 C (rem) (B) 05 Jm 500 A taken hen time oxidostion Ty O.075 o1103 for wet oxidatin Now 2.05 .6.17 XJ0X127 3 (1-63 X 108) e et A um 1242 4 8.617 7101273 (BJwet 386 X e O 31266 Bwet

da ken for the rest o.95 uM time uing 6xtd wet oxidation 2 B 0.95 0.312 66 ト243 2 08-40176 3I64 hr oxidasion 1 un tie taken fir Todel a.90 h04 3'64 hr 4 .54 hr A