EE 143 MICROFABRICATION TECHNOLOGY SPRING 2010 C Nguyen PROBLEM SET 4 Issued Thursday Feb 18 2010 Due Thursday Feb 25 2010 7 00 p m in the EE 143 homework box in 240 Cory 1 In HW 2 you created a process flow for fabricating a pn diode of which the cross section and the four layer layout are shown below Al Al n p SiO2 P substrate Al lines mask IV DF A n implant mask I DF A Contact mask III DF DF dark field p implant mask II CF CF clear field Process flow 1 Lithography of n implant mask I dark field 2 Ion implantation P n type 3 Remove photoresist 4 Lithography of p implant mask II clear field 5 Ion implantation B p type 6 Remove photoresist EE 143 MICROFABRICATION TECHNOLOGY SPRING 2010 C Nguyen 7 Silicon oxidation target 300nm 8 Lithography of contact mask III dark field 9 Etch SiO2 10 Remove photoresist 11 Sputter Al target 500nm 12 Lithography of Al lines mask III dark field 13 Etch Al 14 Remove photoresist each lithography step consists of spin expose and develop photoresist a What type of photoresist positive or negative must be used on each of the four lithography steps b In order to pattern Al metal lines the lift off process may be used instead of using the etching process described in step 11 to 14 Replace step 11 to 14 described above with the two layer photoresist lift off process shown as below i ii iii iv v vi Spin on 1 1 m g line photoresist Expose without any mask Spin on 1 1 m g line photoresist Contact lithography mask IV dark field expose and develop Evaporate Al target 500 m Remove photoresist in acetone Draw the cross sections along AA plane through step iv v and vi Ignore the patterns made prior to the metal definition i e start with a blank wafer for the lift off process 2 Problem 3 2 3 8 3 10 3 12 in the textbook Jaeger
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