《Microelectronics Process》Sputter deposition

3.155J6.152J Microelectronic Processing Technology Fall Term. 2003 Bob HAndley Martin schmidt Problem set 6 Out Nov, 12. 2003 Due no,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> I 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 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%o for your chosen conditions? Some possibly useful information is shown below Q 8 ○○○OC

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. It is very difficult to evaporate stoichiometric SiO2; you often get SiO, with 1 <x<2, which implies a mixture of SiO and Sio2. But you still need to get as close as possible to SiO2 a) What partial pressure of O2 must you have in your vacuum chamber so that the flux of O, on the substrate is the same as that of si? y our evaporation source has a surface area of I cm the substrate is at a planetary radius of 20 cm, and your crucible is heated to 1500C b) What is the mean free path of O, 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?

2 † 2. It is very difficult to evaporate stoichiometric SiO2; you often get SiOx with 1 < x < 2, which implies a mixture of SiO and SiO2. But you still need to get as close as possible to SiO2. a) What partial pressure of O2 must you have in your vacuum chamber so that the flux of O2 on the substrate is the same as that of Si? Your evaporation source has a surface area of 1 cm2 , the substrate is at a planetary radius of 20 cm, and your crucible is heated to 1500o C. b) What is the mean free path of O2 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?