EE 143 MICROFABRICATION TECHNOLOGY SPRING 2010 C Nguyen PROBLEM SET 2 Issued Thursday Feb 4 2010 Due Thursday Feb 11 2010 7 00 p m in the EE 143 homework box in 240 Cory I Process Flow Layout to Cross Section 1 Consider the cross section of a device shown below a What kind of device is this b Generate a possible process flowchart for fabrication of this structure Use a form like the cross sections in Figure 1 6 in Jaeger s textbook Al Al n p SiO2 P substrate 2 Consider the following layout of two MOSFET devices and the corresponding process flow W W A A L Device A N well Active L L L Device B Poly Si P N Contact Metal EE 143 MICROFABRICATION TECHNOLOGY SPRING 2010 C Nguyen The process flow 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Silicon oxidation target 300nm Lithography Mask I N well Etch SiO2 Remove PR N well diffusion P n type Etch SiO2 Silicon oxidation target 100nm LPCVD Si3N4 target 500nm Lithography Mask II Active Etch Si3N4 Etch SiO2 Field isolation implant B p type Remove PR Grow 1 m of SiO2 thermally LOCOS oxidation Etch Si3N4 Etch SiO2 Dry oxidation for gate oxide target 100nm LPCVD situ phosphorous doped gate polysilicon target 350nm Lithography Mask III Poly 20 Dry etch polysilicon 21 Remove PR 22 Lithography Mask IV n implant dark field 23 D S ion implantation P n type 24 Remove PR 25 Lithography Mask V p implant clear field 26 D S ion implantation B p type 27 Remove PR 28 Anneal at 1050 C to activate dopants and drive in diffusion 29 LPCVD PSG target 1 m and reflow at 950 C 30 Lithography Mask VI contact 31 Etch SiO2 down to S D regions 32 Remove PR 33 Deposit Al sputtering target 1 m 34 Lithography Mask VII metal 35 Dry etch Al a Plot the cross sections along AA plane through step 6 14 21 26 and 35 b A MOSFET device can be represented by a circuit symbol view e g a NMOS device layout can be depicted as W L W L Draw the circuit schematics implemented by each device layout in A and B Then for each of A and B equate the circuit to an equivalent single device and redraw the layout so that it realizes the corresponding single device
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