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[問題求助] 元件模型在IC設計產業的角色

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發表於 2016-12-2 03:03:34 | 顯示全部樓層 |閱讀模式
A top-down design approach in IC industry comprises of three levels which includes:
9 B* e* x+ l1 L8 c1 tIC design (circuit-level), model / device(device-level), IC process technology(fabrication-level).0 n* n( T0 N+ n) Z
On the circuit-level, % A8 d! S4 Y) w5 p
a compact model provides the external terminal electrical characteristics / I- }" w: |: k. s1 C1 [
resulted from the mathematic expressions of an electronic device.2 x/ f, v4 E. l! x6 N2 U4 L. d/ l
The external terminal characteristics (Pin Characteristics) includes terminal voltages, currents or charges, ! D9 P  s* s0 T2 D" T, [8 W
are featured as the input and output ports values.1 ^, |9 T1 \$ T5 w0 a- y  `1 R
The unknown ports values of a device are solved by a simulator when performing circuit analysis.9 F+ r0 Q' F5 [8 B% R4 e
After the structure and behavior of the individual compact model is specified, the description(structure and behavior) are
$ ^- N$ \2 i: i, X) X- r2 p% usubmit to the simulator. The simulator employees KCL and KVL to create a set of nonlinear equations.
: c* z1 M3 {$ V+ RThe nonlinear differential equations are not solved directly, but with approximation and iterative methods. Under certain # d3 H* h  h/ B4 a
approximation, the equations are solved with the Newton-Raphson method. The solutions are equilibrium points of nodal analysis.9 R6 H: d& m2 S* S1 c3 n  x
IC design engineers work on a higher abstraction level than the device(transistor) level.0 G6 I. z6 {+ P9 q+ R
In other words, transistors are the primitive components in the eye of IC designer.
7 s. J$ u# Q! n+ o. n: a) Q& a/ OA virtual symbol is the representive of a real device(component).
" S' K' K6 s0 z  A0 bFor instance, transistor's compact model is seen as a 4 pins symbol.
9 ?* w# U3 z8 ~In Advanced Design System(ADS),  three design types are allowed: schematic, symbol, and layout.
9 g7 Q2 L4 O5 t; B3 Z' `; G3 iThose designs can all be stored in a small containner names "cell" and a big containner names "library".
& G" e/ ]+ U8 C) g6 U; }( w2 JIC designer works with the connection of some symbols in a schematic.
' d/ X  q- @1 f8 m1 m1 Y6 ZEach symbol represents an electronic device (component).
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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. 6 L& {% {& Y% {7 ]  s1 `' s
On the fabrication-level, $ ~! B5 E) \3 E- M$ C$ A
a compact model has the internal description of the device characteristics by means of a set of physics-based expressions with " w4 j! f6 |) i. P) V. y
technology dependent model parameters. The physic-based model parameters values accounts for the actual behavior and properties
* m9 S) e. f# J* \" v7 c6 Uof a device are defined by its process variables such as: geometrical dimensions and doping profiles.
8 ?; B- x, g) X; EThe true parameters values need to be carefully measured by the experimental setup of device characterization.
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the verified compact models are expected to be implemented in simulators.! n2 b$ i) ~5 @7 C# C
Thus the modelling accuracy and computational efficiency that a simulator can provide to integrate circuits' analysis
) d& w& p! A# Eis 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.
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