EECS 105 Fall 2001 Lecture 9 R T Howe Lecture 9 Last time Compensation Drift current density Today IC resistors Metal metal capacitors start Dept of EECS University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe Resistivity Bulk silicon uniform doping concentration away from surfaces n type example in equilibrium no Nd When we apply an electric field n Nd J n q n nE q n N d E Resistivity n Dept of EECS University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe Ohm s Law Current I in terms of Jn Voltage V in terms of electric field Result for R Dept of EECS University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe Sheet Resistance IC resistors have a specified thickness not under the control of the circuit designer Eliminate t by absorbing it into a new parameter the sheet resistance L L L Rsq R Wt Dept of EECS t W W University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe Using Sheet Resistance Ion implanted or diffused IC resistor Dept of EECS University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe Idealizations Why does current density Jn turn What is the thickness of the resistor What is the effect of the contact regions Dept of EECS University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe IC Capacitors Metal layers separated by insulators get intentional or parasitic capacitor Metal 2 Metal 1 C Dept of EECS dielectric d td University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe Metal Metal Capacitor Layout A A 1 Overlap area A12 A A 2 Dept of EECS University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe Circuit Model Capacitance between metal 1 and metal 2 C12 d td A12 Other capacitors what is terminal 3 Dept of EECS University of California at Berkeley EECS 105 Fall 2001 Lecture 9 R T Howe Surface Charge and Electric Field 0 V td x Q C cm2 Q td x Dept of EECS V University of California at Berkeley
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