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: ) P8 a( w, i$ K0 w8 j, M5 @IC design (circuit-level), model / device(device-level), IC process technology(fabrication-level).! Q c) Q+ K7 {/ _ h# Y
On the circuit-level, & U( g4 g) A! c& F5 V- Y$ a( W' I
a compact model provides the external terminal electrical characteristics ) C) t( [8 L5 J6 @, N3 E! W' u
resulted from the mathematic expressions of an electronic device.+ x( f! {' k+ e0 p6 j2 n |3 g: H
The external terminal characteristics (Pin Characteristics) includes terminal voltages, currents or charges, & ~0 q: ? h6 z5 b
are featured as the input and output ports values.& u# A. J, }5 v, N' c' |* \
The unknown ports values of a device are solved by a simulator when performing circuit analysis. 9 M$ k; S3 n. V( q/ f8 U; L( _6 wAfter the structure and behavior of the individual compact model is specified, the description(structure and behavior) are 4 n5 F, i2 x" a0 n4 \ osubmit to the simulator. The simulator employees KCL and KVL to create a set of nonlinear equations. + M5 j1 g9 B& ?4 u5 LThe nonlinear differential equations are not solved directly, but with approximation and iterative methods. Under certain 5 r% u% ?5 G+ A. ]9 C% M2 K
approximation, the equations are solved with the Newton-Raphson method. The solutions are equilibrium points of nodal analysis. + Y/ Y# L; E/ }6 v' J9 g! m& _3 m3 ZIC design engineers work on a higher abstraction level than the device(transistor) level.$ f# s' i0 ?0 i6 V2 }, w. P
In other words, transistors are the primitive components in the eye of IC designer. 9 G% A; x! h4 ^A virtual symbol is the representive of a real device(component).. i( E1 a* ^* J+ f" }4 f& W
For instance, transistor's compact model is seen as a 4 pins symbol. 4 \% ]& b3 @: G& {. M
In Advanced Design System(ADS), three design types are allowed: schematic, symbol, and layout. ' P; e' v% }2 nThose designs can all be stored in a small containner names "cell" and a big containner names "library". ; {, @1 A0 P5 ~$ a1 z9 mIC designer works with the connection of some symbols in a schematic. " z' B8 ^5 d# _+ W, `9 L% Q L" @Each symbol represents an electronic device (component). ! z- I0 E9 L$ ?! u7 B. H 2 H7 S; s2 X9 k$ O; J! L # V# C, f; I4 N4 T ( t8 ]# z% n( c8 C$ ]+ q& ^& GLittle 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. ; S# O2 r ?8 L+ b4 BOn the fabrication-level, % G1 K; t6 J7 Y0 Oa compact model has the internal description of the device characteristics by means of a set of physics-based expressions with # s: r- b _2 ntechnology dependent model parameters. The physic-based model parameters values accounts for the actual behavior and properties 9 k" B7 [! \4 R1 M$ Q3 c8 Lof a device are defined by its process variables such as: geometrical dimensions and doping profiles.) y% U6 i% `# |: }! X; V
The true parameters values need to be carefully measured by the experimental setup of device characterization. : e! o( z! ?1 j( f- A5 _7 g
Accordingly, ) G- d$ j! M9 y; F( a1 T& ^! x2 mthe verified compact models are expected to be implemented in simulators.( B( y3 T8 g' y# S7 w9 e+ G
Thus the modelling accuracy and computational efficiency that a simulator can provide to integrate circuits' analysis 8 A# a- z7 q; _
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. 1 N9 ^4 ?$ S7 {8 O. m; ], g 1 _3 B- C! U e3 e * X9 b4 o/ w* X$ N, t ' o( K% X2 k, C. s# d# C; Q0 [# y* U" |2 @+ E3 G+ L" b
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