標題: 元件模型在IC設計產業的角色 [打印本頁] 作者: DaShiaSun@FB 時間: 2016-12-2 03:03 AM 標題: 元件模型在IC設計產業的角色 A top-down design approach in IC industry comprises of three levels which includes: 6 O+ _# H; q1 y5 m! v; s
IC design (circuit-level), model / device(device-level), IC process technology(fabrication-level). / |; V7 t- q, y4 F* _On the circuit-level, $ D3 S: A: L; H: | p! `4 p) ]1 Ca compact model provides the external terminal electrical characteristics 5 m" D1 X1 A1 I! R1 E
resulted from the mathematic expressions of an electronic device.5 M/ U9 O+ y: y
The external terminal characteristics (Pin Characteristics) includes terminal voltages, currents or charges, ( O. E9 J4 d' C6 Y- G* B P4 x! V" N& ~
are featured as the input and output ports values.* q$ }6 q# r E& q
The unknown ports values of a device are solved by a simulator when performing circuit analysis.' c, o: x' d) h. ]% r! `, k4 }
After the structure and behavior of the individual compact model is specified, the description(structure and behavior) are 8 c* O9 _/ k, G2 x5 w8 g2 R- B3 a# o
submit to the simulator. The simulator employees KCL and KVL to create a set of nonlinear equations. 5 W5 i1 E% Z; G- G8 d& O, wThe nonlinear differential equations are not solved directly, but with approximation and iterative methods. Under certain : L+ e! j, m9 u* V& r3 K7 g
approximation, the equations are solved with the Newton-Raphson method. The solutions are equilibrium points of nodal analysis.7 F% p: y: |% p
IC design engineers work on a higher abstraction level than the device(transistor) level. " t' C5 `3 D! b5 @; B' mIn other words, transistors are the primitive components in the eye of IC designer.1 h. s: ]7 N1 m
A virtual symbol is the representive of a real device(component). . g- A8 a" I0 o3 NFor instance, transistor's compact model is seen as a 4 pins symbol. 4 T) l/ g4 I; t: k. g" }+ ^& kIn Advanced Design System(ADS), three design types are allowed: schematic, symbol, and layout.* v3 k# v0 t4 k" f( l. s$ Q
Those designs can all be stored in a small containner names "cell" and a big containner names "library". " |. {5 K. t$ P4 @, ^IC designer works with the connection of some symbols in a schematic. / e! g! f5 v3 F: UEach symbol represents an electronic device (component). 7 j6 K9 O" e% Z; J3 x " @) C: f! n; t$ n9 c, H# J+ F ( X$ x2 @$ {- i+ I: k! V7 {" o" B: M4 Y# g3 @
Little knowledge of a device's internal structures and behaviours are required for IC designers. Because a device works as a funtional block. In stead, a device's external structures (connection) and behaviours are of concerns. 4 _! J- _2 p7 t" d7 S" aOn the fabrication-level, % ^4 B4 H; j5 h0 @9 E! ha compact model has the internal description of the device characteristics by means of a set of physics-based expressions with - {$ B$ j v8 [+ O+ ~technology dependent model parameters. The physic-based model parameters values accounts for the actual behavior and properties , N+ T6 i# t I* m, ~$ c( iof a device are defined by its process variables such as: geometrical dimensions and doping profiles. ! B/ I! F5 ^4 { iThe true parameters values need to be carefully measured by the experimental setup of device characterization. ) O8 w; _/ i, l5 vAccordingly, " g" R# s: _0 j- ~6 _. E8 }3 ~
the verified compact models are expected to be implemented in simulators. # l% E; ]# U+ y2 Z2 V. Q: ^Thus the modelling accuracy and computational efficiency that a simulator can provide to integrate circuits' analysis " W* k( I( I8 o6 g$ l2 p. _is the same as its implemented compact model. Meanwhile, a compact model is the most crucial process design kit, which plays as the interface between circuit designers and device developers. 9 @2 C/ n' p& e \) i/ s ! p* G, A; q% j& d, k% t4 X( ]% r' u2 T# K& t+ `$ c" M; F- M, Y* O2 o' B1 b9 F
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