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: # N/ @9 I* Z0 Y' S q) O6 N
IC design (circuit-level), model / device(device-level), IC process technology(fabrication-level). 9 S/ c- m7 c2 S: p1 iOn the circuit-level, ' M/ L4 q% F- h7 U7 ?0 Wa compact model provides the external terminal electrical characteristics / b% \4 g) j$ c+ C
resulted from the mathematic expressions of an electronic device.7 q) _! v- } O" R
The external terminal characteristics (Pin Characteristics) includes terminal voltages, currents or charges, ) k( u7 h. I5 X W: ]2 zare featured as the input and output ports values. . A8 @" X* f. e1 s8 R1 Q, J0 j! v( AThe unknown ports values of a device are solved by a simulator when performing circuit analysis.6 Q% J0 ]4 b0 t
After the structure and behavior of the individual compact model is specified, the description(structure and behavior) are # F" x/ R# q* A3 K' n( H& _6 ?! jsubmit to the simulator. The simulator employees KCL and KVL to create a set of nonlinear equations. + \* b x6 Z+ I! F6 q) ^The nonlinear differential equations are not solved directly, but with approximation and iterative methods. Under certain " H* Y |. S A3 p8 g
approximation, the equations are solved with the Newton-Raphson method. The solutions are equilibrium points of nodal analysis.( z/ |4 i- c7 H# c% R1 d
IC design engineers work on a higher abstraction level than the device(transistor) level.% s/ }; i, m# t {- P* D$ l. f
In other words, transistors are the primitive components in the eye of IC designer.( c9 }1 a8 e; A( ~0 f
A virtual symbol is the representive of a real device(component). ! B& n: w7 t# H yFor instance, transistor's compact model is seen as a 4 pins symbol. % V! a, [' C# K* S
In Advanced Design System(ADS), three design types are allowed: schematic, symbol, and layout. ( @ h6 q+ Y. z$ P, Q6 pThose designs can all be stored in a small containner names "cell" and a big containner names "library". % l) m# Q3 z- N# L6 T0 t
IC designer works with the connection of some symbols in a schematic.$ O h9 d8 }6 z% [0 e
Each symbol represents an electronic device (component). 3 F: @+ b8 W- I/ h$ w
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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. / H$ W& C1 K) d: G6 u' q; GOn the fabrication-level, - b& ^$ g) T( k. j: o& Sa compact model has the internal description of the device characteristics by means of a set of physics-based expressions with 3 S# G1 l3 D/ j) Y5 D, [/ ttechnology dependent model parameters. The physic-based model parameters values accounts for the actual behavior and properties ) a' S; P5 U9 d/ B- g: M
of a device are defined by its process variables such as: geometrical dimensions and doping profiles. 7 {8 C' C# T5 W6 MThe true parameters values need to be carefully measured by the experimental setup of device characterization. 0 M6 z7 [0 \! s" q+ R! m5 @7 T, F
Accordingly, 7 n/ P7 b* F- M e+ n0 e& C
the verified compact models are expected to be implemented in simulators. & x% G$ o5 O0 K, h$ E9 _Thus the modelling accuracy and computational efficiency that a simulator can provide to integrate circuits' analysis ; Q" ^0 o5 u. N0 O0 k. G$ T, q: P9 M
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. , J+ R% O+ |, r- {, b% M. a9 @1 J " ]5 S5 ~9 Y2 i# U6 R ) ?; x" y' E6 ` p( ~% t3 O. M4 H) p , B/ p+ R& B3 _ , `/ X( ^1 ]' |3 s0 N7 w & _$ r* q0 c3 k- h$ {3 h# t# \0 ?# v, ^7 a. M0 B
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