1. Microfabrication Home exercise 1
Deadline for returns 22th January, 2017, 10 pm into MyCourses return box 1.

2. Q1: Silicon doping level
a) Consider an Olympic swimming pool filled with golf balls (representing silicon atoms) and one squash ball (representing boron dopant). If a silicon wafer had similar doping concentration, what would be its resistivity? Hint: Use Fig. 4.1 for doping vs. resistivity conversion.
b) Typical oxygen concentration in silicon is 15 ppma (parts per million atoms). If cricket balls represent oxygen atoms, how many of them should be found in our swimming pool ?
Note: this is an order of magnitude exercise: use single digit accuracy only, e.g. 2 cm radius and give doping level as e.g. 8*1019 cm-3.

3. Q2: Thermal oxidation
a) If 250 minute wet oxidation results in 1 µm thick oxide, how long will it take to grow 5 µm oxide under same conditions?
b) How long will it take to grow 200 nm thick oxide?
Hint: Use the parabolic assumption, figure 13.3.

4. Q3: Ion implantation
a) 150 mm diameter wafers are implanted with 100 µA current of B+ ions. How long does it take if the dose is 1014 cm-2 ?
b) If CMOS source/drain areas are implanted with 1015 cm-2 dose and the depth is 200 nm, what is the doping concentration in those areas ?

5. Q4: Oxides
Explain the main similarities and differences between thermal oxide and CVD oxide.

6. Q5: FLEEESLESLEES… Spot exercise 1 revisited:
Provide a letter sequence fabrication process for them !
L = Lithography
E = Etch
F = Film deposition
S = Strip resist

7. Q6: Thermal oxidation
Draw where 200 nm thick thermal oxide will grow in the structure shown below. Detail drawing needed; no points for hasty sketches. For once, this drawing is to scale: the trench width is 1 µm, poly is 500 nm thick, and so on. (However, n+ substrate is 500 µm thick). Hint: take a photo and copy-paste into your document.