Resistors - Microelectronic Devices and Circuits - Solved Exam, Exams of Microelectronic Circuits

Download Resistors - Microelectronic Devices and Circuits - Solved Exam and more Exams Microelectronic Circuits in PDF only on Docsity! University of California at Berkeley College of Engineering Dept. of Electrical Engineering and Computer Sciences EE 105 Midterm! Spring 2002 Prot. Roger T. Howe March 6, 2002 Guidelines Closed book and notes; one 8.5" x 11” page (both sides) of your own notes is allowed. You may use a calculator. Do not unstaple the exam. Show all your work and reasoning on the exam in order to reecive full or partial credit. Score Points | Problem | Possible Score 1 17 2 17 3 16 Total 50 1. IC resistors [17 points] ‘Oxide Mask Contact Mask {dark field) & (dark field) Polysilicon Mask [7 Metal Mask (clear field) (clear field) 0 yen ol l ry Wy Vi BU Process Sequence: le 1. Starting material; p-type silicon wafer with a doping concentration of |x 10 em 2, Deposit a 250 nm-thick SiO: layer 3, Deposit a 250 nm-thick layer of n-type polysilicon and pattern using the Polysilicon Mask (clear field). 4. Pattern the oxide using the Oxide Mask (dark field). 5. Implant phosphorus with dose Qy— $5 x 10!* om? and anneal to form a 250 nm thick phosphorus-doped region, 6. Deposit a 250 nm-thick SiO» layer and pattern using the Contact Mask (dark field). 7, Deposit 0,5 parof aluminum and pattern using the Metal Mask (clear field). 250 nw ia 2. MOS charge-storage element [17 pts.] A = } P re Ts (0) By fer) Bz f ———. 8 pm ——>|4¢——- 8 sm ——_>} Uff LITLE LL MLL LL! B, The MOS structure shown in cross section and top view above has a metal gate and two. bottom electrodes, B; (p substrate) and Bz (n' layer). The bottom electrodes are contacted by a metal line and shorted together, as indicated on the top view. The oxide thickness is fox =H for the MOS structure. Gy = 2.45x)07 3 Pham, WS In region 1, the p-type substrate is the bottom electrode and the MOS parameters are: Vra=-1.2 V, Fr = 0.8 V In region 2, the n’ layer is the bottom electrode and the MOS parameters are: Vey =-0.2.V, Vy =-3V ‘The charge storage curves for the two regions are provided on the graphs below of gate charge per unit area versus the gate-bottom electrode potential, veg. Since By) = Bo, we use “B” to represent the potential of the bottom electrode for each region. Region | ecettarvee ROCHON 2: (a) [4 pts] For vag = | V, find the total charge on the gate (units: femtoCoulombs = 1076), fe, ™ i - , . an Gt fo | Pine = Fo *Ia* = & fe fu Mba apt) + (3 fe find XBxidpm) —_——F (421m | (8 ope0) G@=b72f6 | | Lee (2Fo pe) (b) [4 pts.] For vga =-1.5 V, identify the substrate charge in regions 1 and 2 by circling the correct description(s). Note: the correct answer may have more than one description circled. Region |. ionized aceeptors decumulated holes) inversion-layer electrons Region 2. Gnized donor accumulated electrons inversion-layer holes (c) [4 pts.] For vax = +1.5 V, identify the substrate charge in regions 1 and 2 by circling the correct description(s). Note: the correct answer may have more than one description circled. Region 1. accumulated holes Region 2. ionized donors inversion-layer holes (d) [3 pts.1 Ef we apply a voltage vee () = 0 V + voscos(ar), where ¥es=5 mV and © = 2n(10°) rad/s, estimate the current i,g(1) into the gate terminal in nA from the charge-storage curves. 3.45% 40"! Bee. “ty = Cy Me = te Hips xed tan) = 2bE FF (ido) Ge ~ HOP fF. e ie, 25 fen e Mpls Ge, = Fhe fr 2 (SO) (tnt) = 208 (149) by Par tobi lenv) (408 FF) ) -euveot = (2.84) arnt (595) Cit) (e) [2 pts.] The maximum capacitance of the MOS structure is Ciax. If the DC component of vgris 1.5 V, what is the maximum amplitude of its small-signal somponcnt vp for which the current remains exactly proportional to Cax-