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: : L8 p+ e' E tIC design (circuit-level), model / device(device-level), IC process technology(fabrication-level)., ^5 Q& ~$ l4 ]) ]" R
On the circuit-level, 9 q) b6 A) B2 z* s, ^: s- T
a compact model provides the external terminal electrical characteristics ' D; N4 F2 B/ b, p$ Z' Qresulted from the mathematic expressions of an electronic device. & `4 t' ^( d$ x% p4 _. FThe external terminal characteristics (Pin Characteristics) includes terminal voltages, currents or charges, ( j* s( @4 z8 K( I% @# M6 D# z" aare featured as the input and output ports values.4 w7 E! m( t2 w$ B$ O6 b4 l
The unknown ports values of a device are solved by a simulator when performing circuit analysis.6 D# V9 [6 y4 {7 r% x+ H& }
After the structure and behavior of the individual compact model is specified, the description(structure and behavior) are , H/ \1 y- n5 {' v8 H8 \ g& _$ }
submit to the simulator. The simulator employees KCL and KVL to create a set of nonlinear equations. ) h$ F1 A3 I L6 u, S, D
The nonlinear differential equations are not solved directly, but with approximation and iterative methods. Under certain _$ N9 Q" z$ [4 p8 E
approximation, the equations are solved with the Newton-Raphson method. The solutions are equilibrium points of nodal analysis. 9 p: W7 V+ U8 n+ \IC design engineers work on a higher abstraction level than the device(transistor) level. ! F8 w5 v9 z$ E- r& G% c EIn other words, transistors are the primitive components in the eye of IC designer.( ?0 m' {+ y# ]5 z; m; H0 L" O7 U
A virtual symbol is the representive of a real device(component).% d, T- B" I/ [$ c& ]
For instance, transistor's compact model is seen as a 4 pins symbol. + b" h3 _& n8 o4 b. x% @9 x
In Advanced Design System(ADS), three design types are allowed: schematic, symbol, and layout.: }* T6 @9 A$ Q
Those designs can all be stored in a small containner names "cell" and a big containner names "library". , e* N# Y2 [% Y4 t3 ^IC designer works with the connection of some symbols in a schematic.$ }- u' T; l/ } o6 I, \5 ]0 z/ I$ L* [; u
Each symbol represents an electronic device (component). 4 w* B& x: q* w % P$ C! b% X5 s" S2 T8 A5 c/ v: K+ A2 ~) m, }4 I! H; W8 O
: I# e* J8 N3 z# b2 f% F1 b0 t6 RLittle 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 v! y7 l; W( x$ z8 n
On the fabrication-level, ; z/ h$ b7 a" y% s# Q
a compact model has the internal description of the device characteristics by means of a set of physics-based expressions with 3 H2 r, s5 I$ G4 [+ `% o7 X$ r
technology dependent model parameters. The physic-based model parameters values accounts for the actual behavior and properties 2 p+ ~2 Y1 Q7 r; w: A, eof a device are defined by its process variables such as: geometrical dimensions and doping profiles. $ G- }* o% Z8 F+ l. m5 {& z9 nThe true parameters values need to be carefully measured by the experimental setup of device characterization. & g8 I0 j" a3 U' D: ^5 G. Q
Accordingly, & d% D6 j! b! y; T& z+ P
the verified compact models are expected to be implemented in simulators." p. J2 k$ Z2 d, s
Thus the modelling accuracy and computational efficiency that a simulator can provide to integrate circuits' analysis : E, A0 E X8 T0 ~. Z6 U O0 o
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. 4 f: Q( V8 K/ ]/ o% y" n8 L1 U$ O% J
! h; B/ u( ?4 W- f! B
: y: f# v. U' i' t9 q' ^
& N" A2 c7 Z3 E# j- M; @0 r
- f, w2 x$ m7 J
; y0 G9 J: W5 M2 [4 l; y' } + G* C5 ` C/ ?5 O6 B9 k: q4 d f' Y4 w @4 a5 ]/ N" [* w4 @0 l) N 7 n8 o7 Q6 ^7 l$ N' N! _$ t! C( f( L & }, D: j# i' D- b