ELEC0029 - Practice Problem Sets for Topics 1-2 and 1-3
Topics 1-2 – Silicon Wafers
1. Take a close look at Silicon. What is its valence band structure? How many outer
electrons does it have which are involved in crystalline binding? In which
column of the Periodic table does it reside? Which elements are used as donor
and acceptor atoms during doping? What is the difference between mono-
crystalline, poly- crystalline and amorphous silicon? What is meant by p-type
silicon? by n-type silicon?
2. How is natural silicon made into metallurgical grade silicon? What other element
is introduced into the process to purify the natural carbon? What is the chemical
reduction formula? How much energy is needed and how is that energy
introduced in the process?
3. What are the steps involved in purifying silicon from metallurgical grade to
electronic grade silicon? Which elements are introduced to the process and what
is the chemical reduction formula? How pure is the silicon when finished?
4. Describe in detail the Czochralski process for growing EGS. Include a sketch of
the apparatus used. Do the same with the Float-Zone process.
5. The ratio of the concentration of dopant in the solid to the dopant’s original
concentration in the melt is 0.40 (40%). Find its segregation coefficient in the
Topic 1 slides and calculate the percentage of melt that has solidified. See if it
matches the figure, also on the slides.
6. The segregation constant of a particular dopant to be used in a CZ process is
0.80. Suppose at the end of the pull, the solid is to have half the mass of the
original melt.
(a) What is the ratio of the mass of the solid to the mass of the melt 1/3, 1/2,
and 3/4 of the way through boule growth?
(b) What is the ratio of the dopant concentration in the solid ingot to the
original concentration of the initial melt at each point in the process?
(c) Draw the curve Cs/Co vs M/Mo.
7. What are the steps involved in the float-zone process? If the process is to work,
within what value range must the separation constant be?
8. Make drawings showing the three planes that are commonly grown in the boule
for semi-conductors. Show drawings of how a boule is labelled so that its plane
of orientation can be identified.
Topics 1-2 – Silicon Wafers
1. Take a close look at Silicon. What is its valence band structure? How many outer
electrons does it have which are involved in crystalline binding? In which
column of the Periodic table does it reside? Which elements are used as donor
and acceptor atoms during doping? What is the difference between mono-
crystalline, poly- crystalline and amorphous silicon? What is meant by p-type
silicon? by n-type silicon?
2. How is natural silicon made into metallurgical grade silicon? What other element
is introduced into the process to purify the natural carbon? What is the chemical
reduction formula? How much energy is needed and how is that energy
introduced in the process?
3. What are the steps involved in purifying silicon from metallurgical grade to
electronic grade silicon? Which elements are introduced to the process and what
is the chemical reduction formula? How pure is the silicon when finished?
4. Describe in detail the Czochralski process for growing EGS. Include a sketch of
the apparatus used. Do the same with the Float-Zone process.
5. The ratio of the concentration of dopant in the solid to the dopant’s original
concentration in the melt is 0.40 (40%). Find its segregation coefficient in the
Topic 1 slides and calculate the percentage of melt that has solidified. See if it
matches the figure, also on the slides.
6. The segregation constant of a particular dopant to be used in a CZ process is
0.80. Suppose at the end of the pull, the solid is to have half the mass of the
original melt.
(a) What is the ratio of the mass of the solid to the mass of the melt 1/3, 1/2,
and 3/4 of the way through boule growth?
(b) What is the ratio of the dopant concentration in the solid ingot to the
original concentration of the initial melt at each point in the process?
(c) Draw the curve Cs/Co vs M/Mo.
7. What are the steps involved in the float-zone process? If the process is to work,
within what value range must the separation constant be?
8. Make drawings showing the three planes that are commonly grown in the boule
for semi-conductors. Show drawings of how a boule is labelled so that its plane
of orientation can be identified.
