technology computer-aided design

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Technology Computer-Aided Design (TCAD) refers to using computer simulations todevelop and optimize semiconductor processing technologies and devices. TCADsimulation tools solve fundamental, physical, partial differential equations, such asdiffusion and transport equations for discretized geometries, representing the siliconafer or the layer system in a semiconductor device. This deep physical approach givesTCAD simulation predictive accuracy.

Therefore, it is possi!le to su!stitute TCAD computer simulations for costly and time-consuming test afer runs hen developing and characterizing a ne semiconductordevice or technology.

TCAD simulations are used idely in the semiconductor industry. As technologies!ecome more comple", the semiconductor industry relies increasingly more on TCAD tocut costs and speed up the research and development process. #n addition, semiconductormanufacturers use TCAD for yield analysis, that is, monitoring, analyzing, andoptimizing their #C process flos, as ell as analyzing the impact of #C process variation.

TCAD consists of to main !ranches$ process simulation and device simulation.

#n process simulation, processing steps such as etching, deposition, ion implantation,

thermal annealing, and o"idation are simulated !ased on physical equations, hichgovern the respective processing steps. The simulated part of the silicon afer isdiscretized (meshed) and represented as a finite-element structure (see %igure &).

For example, in the simulation of thermal annealing, complex diffusion

equations for each dopant species are solved on this mesh. For oxidation

simulations, the growth of silicon oxide is simulated taking into

account the oxygen diffusion, the mechanical stresses at corners, and so

on.TCAD consists of to main !ranches$ process simulation and device simulation.


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1.3 Device Simulation

Device simulations can !e thought of as virtual measurements of the electrical !ehaviorof a semiconductor device, such as a transistor or diode. The device is represented as ameshed finite-element structure. 'ach node of the device has properties associated ithit, such as material type and doping concentration. %or each node, the carrierconcentration, current densities, electric field, generation and recom!ination rates, and soon are computed (see %igure ).

'lectrodes are represented as areas on hich !oundary conditions, such as appliedvoltages, are imposed. The device simulator solves the oisson equation and the carriercontinuity equation (and possi!ly other equations). After solving these equations, theresulting electrical currents at the contacts are e"tracted (see %igure *).

%igure . Current flo lines in a +.&*-m /0%'T at 1gs2 &.3 1 and 1ds2 *.+ 14

shading represents current density.


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used to design, organize, and run simulations for semiconductor research andmanufacturing. 0imulations are comprehensively organized into pro@ects.

A simulation flo typically consists of several tools, such as the process simulator0entaurus rocess, the meshing tool 0entaurus esh, the device simulator 0entaurusDevice, and the plotting and analysis tool #nspect.

0entaurus 5or6!ench automatically manages the information flo from one tool toanother. This includes preprocessing user input files, parameterizing pro@ects, setting upand e"ecuting tool instances, and visualizing the results.

0entaurus 5or6!ench allos you to define parameters and varia!les to runcomprehensive parametric analyses. The use of mathematical and logical e"pressionsserves to preprocess the simulation input dynamically. The resulting data can !e usedith statistical and spreadsheet softare.

%or more information, see the 0entaurus 5or6!ench module.

%igure &. >raphical user interface of 0entaurus 5or6!ench ith a loaded pro@ect. The leftpane shos the pro@ects !roser4 the tool flo of the loaded pro@ect is shon in thecenter4 and the parameter definitions of different e"periments are shon under the toolro. (Clic6 image for full-size vie.)

2.2 Liament

7igament is a generic interface for TCAD process simulations. The 7igamentenvironment is designed to set up and perform TCAD simulations at a high level ofa!straction. #nput files for simulation programs are generated automatically. The systemis integrated into 0entaurus 5or6!ench and or6s ith all 0entaurus tools. The open
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architecture allos for customized modifications and additions of commands or simulatortranslation modules. The comprehensive and clearly arranged process information can !eused for purposes !eyond simulation, for e"ample, the generation of reports.

2.2.1 Liament !low "#itor

The 7igament %lo 'ditor provides a convenient >?# to create and edit process flos. #tis used to assem!le a process flo from macros, including !oth local macros defined !yusers and glo!al macros defined in the 7igament tool li!rary. #t uses the simple processrepresentation (0) language, hich is independent of the language requirement of anyparticular process simulator.

%igure . 7igament %lo 'ditor ith a loaded process flo. (Clic6 image for full-sizevie.)

2.2.2 Liament La$out "#itor

The 7igament 7ayout 'ditor provides a >?# to create and edit layouts. #t is an interface


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!eteen 'DA layout tools and TCAD, and can !e used for defining &D, D, or *Dsimulation domains, or for parameterized stretching of a layout for, for e"ample, 1t roll-off simulations. The 7igament 7ayout 'ditor supports e"ternal layouts in >D0## and C#%format.

%or more information, see the 7igament module.

%igure *. 7igament 7ayout 'ditor ith a parameterized test layout. The to !lac6horizontal lines sho the cutlines that define the D areas for the /0 and /0devices. The !lac6 vertical line defines the parameterization4 the layout is stretched as a

function of the parameter BlgateB.

2.3 Sentaurus %rocess

0entaurus rocess is a comprehensive and highly fle"i!le multidimensional processmodeling environment. Cali!rated to a ide range of the latest e"perimental data usingproven cali!ration methodology, 0entaurus rocess offers unique predictive capa!ilities
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for modern silicon and nonsilicon technologies.

0entaurus rocess includes an interface to 0entaurus 0tructure 'ditor for *D etch anddeposition capa!ilities, a lattice mismatch model for simulating 0i>e and strained silicon,onte Carlo implantation !ased on Crystal-T#, Advanced Cali!ration implantationta!les, analytic implantation and damage models, and state-of-the-art diffusion models.

%urthermore, there is an advanced meshing module (>/A70) !ased on the level-setmethod. >/A70, high-quality anisotropic grids, and the high-performance solverAD#0/ result in e"cellent efficacy and ro!ustness.

The Alagator scripting language used in 0entaurus rocess allos you to develop nediffusion models quic6ly, ma6ing 0entaurus rocess a very convenient tool forcali!ration purposes.

%or more information, see the 0entaurus rocess module.

%igure 8. Animated cross sections of a eometric and process emulation operations can !e mi"ed freely.

%rom the >?#, D and *D device models are created geometrically using D or *Dprimitives such as rectangles, polygons, cu!oids, cylinders, and spheres. Three-dimensional regions also can !e created !y e"truding D o!@ects or seeping D o!@ects

along a path.#n process emulation mode, 0entaurus 0tructure 'ditor translates processing steps, suchas etching and deposition, into geometric operations. #t supports various options such asisotropic or anisotropic etching, deposition, rounding, and !lending to account forspecific processing effects.

0entaurus 0tructure 'ditor offers state-of-the-art visualization. 0tructures are displayed asthey are created and poerful vie filters ma6e it possi!le to select only a su!set ofregions or ma6e certain regions transparent.

Doping profiles and meshing strategies are defined interactively. lacements arevisualized as semitransparent !o"es for easy verification. All doping and meshing optionsof the mesh generation tools 0entaurus esh, esh, and offset*D are supported.

The >?# features a command-line indo, in hich 0entaurus 0tructure 'ditor printsscript commands corresponding to the >?# operations. 0cript commands also can !eentered directly at the command-line indo.

%or more information, see the 0entaurus 0tructure 'ditor module.

%igure 3. >raphical user interface of 0entaurus 0tructure 'ditor. (Clic6 image for full-size
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vie.)

2.' Sentaurus (esh an# )o**set3D

TCAD 0entaurus provides to state-of-the-art approaches for the automatic generation ofmeshes.

0entaurus esh is a modular Delaunay mesh generator of high-quality spatialdiscretization grids for comple" D and *D devices. #t integrates to mesh engines$ thea"is-aligned mesh generator and the tensor-product mesh generator.

The mesh generator offset*D is fully unstructured and pays special attention to meshelements near material interfaces.

oth mesh engines create meshes that can !e used for the discretization methods used inprocess and device simulators. The meshes are adapted not only to the geometry, !ut alsoto the doping concentration in order to capture steep gradients.

%or more information, see the 0entaurus esh moduleand theoffset*D module.

%igure 9. offset*D mesh at the !ac6 of a shallo trench isolation. The gate o"ide isremoved for !etter vieing. The silicon channel area is pin6 and the polysilicon gate,hich dips into the trench, is rasp!erry.

%igure :. 0i>e T ith nitride spacers (gray). /"ide regions are not shon. The dopingprofiles are superimposed on the polysilicon and silicon areas. -doped areas are red, andp-doped areas are !lue. The a"is-aligned mesh is created ith 0entaurus esh.

2.+ Sentaurus Device

0entaurus Device simulates the electrical, thermal, and optical characteristics ofsemiconductor devices. #t is the leading device simulator and handles &D, D, and *Dgeometries, mi"ed-mode circuit simulation ith compact models, and numeric devices. #tcontains a comprehensive set of physical models that can !e applied to all relevantsemiconductor devices and operation conditions.

0entaurus Device is used to evaluate and understand ho a device or6s, to optimizedevices, and to e"tract 0#C' models and statistical data early in the development cycle.

Applications of 0entaurus Device include 1D0 silicon, here 0entaurus Device hasproven accuracy to ell !elo &++-nm technology4 silicon-on-insulator (0/#) devices,here 0entaurus Device is 6non for its ro!ust convergence and accuracy4 dou!le-gateand %in%'T devices, here quantum transport is a reality4 0i>e4 thin-film transistors4optoelectronics4 hetero@unction 'Ts and Ts4 and poer and % semiconductordevices.

%or more information, see the 0entaurus Device module.
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%igure ;. (Top) Animated evolution of current density in an 0/# /0%'T duringe"posure to radiation ith a dose rate of 3+ 6radEs. The device is !iased at 1gs2 + 1 and

1ds2 1. The radiation charges up traps, in particular, in the !uried o"ide (!ron region

at the !ottom). This creates a lea6age path along the silicon-!uried o"ide interface.

Current densities range from F&+-3 Acm-*(!lue) to G&+* Acm-*(red). (ottom) Draincurrent as a function of time during the irradiation.


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2., Tec-lot S

0ynopsys has integrated and customized TecplotH, dedicated softare for scientificvisualization !y Tecplot, #nc., hich has a long history of providing high-qualityengineering and scientific visualization tools. Tecplot 01 is a plotting tool ith e"tensiveD and *D capa!ilities for visualizing data from simulations and e"periments. #trepresents state-of-the-art scientific visualization.

#n addition, it is used to e"plore and analyze data, to produce informative D and *Dvies, to create presentation-quality plots and animations, and to share results on the5e!. The versatility and high-quality output of Tecplot 01 provides you ith totalcontrol to o!tain all types of plot.

%or more information, see the Tecplot 01 module.

%igure raphical user interface of Tecplot 01 shoing electron density in a %in%'Tdevice. (Clic6 image for full-size vie.)

2./ 0ns-ect

#nspect is a plotting and analysis tool for "y data such as doping profiles and electricalcharacteristics of semiconductor devices. The >?# allos for quic6 access to theappropriate curve data. A script language and a li!rary of mathematical functions alloyou to compute ith curves, and to manipulate and e"tract data from simulations. Thee"tracted values can !e returned to 0entaurus 5or6!ench for further applications.
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%or more information, see the #nspect module.

%igure &+. >raphical user interface of #nspect shoing plot of an #dI1gscurve and dialog

!o" for interactive e"traction of the threshold voltage.

2. Calibration it

The Cali!ration =it is a softare pac6age that e"tends the functionality of 0entaurus5or6!ench. #t serves as a data!ase !roser (cali!ration li!raries containing secondaryion mass spectroscopy (0#0) data) and a simulation and pro@ect manager.

The Cali!ration =it assists you to$

erform efficient cali!ration of the process simulators 0entaurus rocess andT0?'-8 in &D.

/!tain a fast, accurate, and relia!le method of evaluating and optimizing processconditions.

?nderstand the sensitivity of processes to various control parameters.

#t allos a predictive analysis of the influence of process equipment parameters onelectrical device data and ena!les you to optimize equipment efficiently.

%or more information, refer to the Calibration Kit User Guide.
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%igure &&. %our e"periments visualized in Tecplot 01. Comparison !eteen e"perimentaldata of implantation (0#0) (red curves), analytic models (green curves on the to uppergraphs), and onte Carlo simulation (green curves on the to loer graphs).

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