1
3.155J/6.152J
Microelectronic Processing Technology
Fall Term,2003
Bob O'Handley
Martin Schmidt
Problem set 6 Out Nov,12,2003 Due Nov,26,2003
Sputter deposition,Read Plummer Chap,9,Sections 9.2.2.2 to 9.3.10,Consider
reading Ohring
1,You need to deposit a high quality (low electrical resistivity) Al film at a very high
rate (v > 1 micron/min) and achieve good step coveage using sputter deposition.
Referring to information in the class notes and text,answer the following three
questions,(Grade will depend more on how you justify your design,rather than on its
correctness – which is harder to determine.)
a) Design,and justify your design,for a sputtering system to deposit this Al with
attention paid to configuration of the anode(s),cathode(s) and substrate placement
(be creative here),as well as the use of DC or RF power source,and biasing,If
possible give some conditions on power requirements and critical dimensions in
the chamber.
b) What sputtering conditions would you use? (type of gas,gas pressure,sputtering
voltage,bias voltage,substrate temperature).
c) Assuming a sticking coefficient of unity for both Al and oxygen,what oxygen
partial pressure could you tolerate in the chamber to keep the oxygen content in
the film less than 1% for your chosen conditions?
Some possibly useful information is shown below:
q
S
90°
2
2,It is very difficult to evaporate stoichiometric SiO
2; you often get SiO
x
with 1 < x < 2,
which implies a mixture of SiO and SiO
2
,But you still need to get as close as possible to
SiO
2
.
a) What partial pressure of O
2
must you have in your vacuum chamber so that the
flux of O
2
on the substrate is the same as that of Si? Your evaporation source has
a surface area of 1 cm
2
,the substrate is at a planetary radius of 20 cm,and your
crucible is heated to 1500
o
C.
b) What is the mean free path of O
2
in this partial pressure (assume the diameter of
an O2 molecule is 0.3 nm).
c) What does your measurement in b) mean for your process?
3.155J/6.152J
Microelectronic Processing Technology
Fall Term,2003
Bob O'Handley
Martin Schmidt
Problem set 6 Out Nov,12,2003 Due Nov,26,2003
Sputter deposition,Read Plummer Chap,9,Sections 9.2.2.2 to 9.3.10,Consider
reading Ohring
1,You need to deposit a high quality (low electrical resistivity) Al film at a very high
rate (v > 1 micron/min) and achieve good step coveage using sputter deposition.
Referring to information in the class notes and text,answer the following three
questions,(Grade will depend more on how you justify your design,rather than on its
correctness – which is harder to determine.)
a) Design,and justify your design,for a sputtering system to deposit this Al with
attention paid to configuration of the anode(s),cathode(s) and substrate placement
(be creative here),as well as the use of DC or RF power source,and biasing,If
possible give some conditions on power requirements and critical dimensions in
the chamber.
b) What sputtering conditions would you use? (type of gas,gas pressure,sputtering
voltage,bias voltage,substrate temperature).
c) Assuming a sticking coefficient of unity for both Al and oxygen,what oxygen
partial pressure could you tolerate in the chamber to keep the oxygen content in
the film less than 1% for your chosen conditions?
Some possibly useful information is shown below:
q
S
90°
2
2,It is very difficult to evaporate stoichiometric SiO
2; you often get SiO
x
with 1 < x < 2,
which implies a mixture of SiO and SiO
2
,But you still need to get as close as possible to
SiO
2
.
a) What partial pressure of O
2
must you have in your vacuum chamber so that the
flux of O
2
on the substrate is the same as that of Si? Your evaporation source has
a surface area of 1 cm
2
,the substrate is at a planetary radius of 20 cm,and your
crucible is heated to 1500
o
C.
b) What is the mean free path of O
2
in this partial pressure (assume the diameter of
an O2 molecule is 0.3 nm).
c) What does your measurement in b) mean for your process?
