Elite 2D Typography Advanced 2D Deposition and Etch Simulator - - PowerPoint PPT Presentation

Elite 2D Typography

Advanced 2D Deposition and Etch Simulator

Elite

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Introduction

• Elite is an advanced 2-D topography simulator for modeling

physical etch, deposition, reflow and CMP planarization processes for modern IC technologies

• Elite provides physics-based, easy to use, and extensible platform

and seamless integrates with SSuprem4 and

• Optolith process simulators within the ATHENA framework

Elite

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Key Benefits

• Predicts the topology evolution during complex processes
• Provides effective alternative for solving processes with

aggressive topographical design rules

• Accurately simulate of critical process issues such as step

coverage, voids, microstructure cracks, etc

• Seamless interface with layout editor MaskViews
• CMP and reflow models provide capabilities to analyze critical

planarization processes

• Additional MC Deposit/Etch module provides several accurate

Monte Carlo based models

• Seamless integrates with SSuprem4

Elite

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Application Examples

• Multi-Level Interconnect
• Metal Step Coverage After Reflow
• Inter-metal Dielectric Void Formation
• Chemical Mechanical Polish
• Microlaoding Effect

Elite

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Multi-Level Interconnect

• Accurate descriptions of

multilevel interconnect structures can be simulated with Elite

• Capability to evaluate the tightly

spaced interconnect lines and dielectric film uniformity of complicated interconnect structures

• The interface with SSuprem4

allows doping and oxidation profiles to be included in the structure

Elite

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Metal Step Coverage After Reflow

• Ability of Elite to model metal step

coverage in a contact via after reflow

• Topographical descriptions such

as this are useful for analyzing and avoiding failure mechanisms during multi-level deposits and patterning steps

• The final structure can be

evaluated in ATLAS

Elite

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Inter-Metal Dielectric Void Formation

• Elite can optimize a process to

avoid formation of superfluous voids during deposition

• Use of two conductors (poly and

aluminum) that come close together

• The narrow gap between them

can form a void as demonstrated in this example

• The type of inter-metal dielectric

material, the thickness of this dielectric, the method of insulation as well as design rules may affect integrity of multi-level metalization

Elite

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Chemical Mechanical Polish

• Elite includes a module for

evaluating effects of CMP processes

• Resulting surface evolution

during a CMP of an inter-metal dielectric layer

Elite

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Microlaoding Effect

• The etch models in Elite

incorporate advanced physical effects such as micro-loading

• Variation in trench depth with

mask window size

Elite

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Elite Models

• Topography processes are modeled by
• Defining a machine in the RATE.DEPO or RATE.ETCH statement
• Running the machine for a specified period of time
• Wet (Isotropic) Etching
• WET and ISOTROPIC parameters in the RATE.ETCH statement
• Reactive Ion Etching (RIE)
• RIE flag and combination of ISOTROPIC, DIRECTIONAL,

CHEMICAL and DIVERGENCE parameters in the RATE.ETCH Statements

Elite

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Elite Models (con’t)

• Deposition with different geometry of material sources
• Unidirectional, Dual Directional, Hemispheric, Planetary, Conical
• ANGLE1[ANGLE,ANGLE3], DEP.RATE, SIGMA.DEP parameters
• Chemical Vapor Deposition (CVD)
• CVD and STEP.COV parameters in the RATE.DEPO statement

Elite

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Elite Models (con’t)

• Monte Carlo Deposition
• To estimate step coverage and film density
• MONTE1/2, ANGLE, SIGMA.DEP, Sticking Coeff. Parameters
• Chemical Mechanical Polishing (CMP)
• Parameters in the RATE.POLISH statement
• REFLOW of glassy silica (oxide, BPSG,etc.)
• Takes place simultaneously with impurity diffusion
• When REFLOW flag set on the DIFFUSE and MATERIAL

statements

Elite

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Interaction of String and Gridding Algorithms

• In Elite, exposed surface is considered as a string of joined points
• During etching or deposition each point of the string advances
• New positions of each point are defined by local etch/deposition

rate

• In contrast to other topography simulators, Elite links the string

with a simulation grid

Elite

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Interaction of String and Gridding Algorithms (con’t)

• During etching, the string cuts through into the grid
• Special regridding algorithm is applied to the area under new

surface

• During deposition, the string advances outside the simulation grid
• Special gridding algorithm is applied to cover newly deposited

area

Elite

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Complex Trench Formation Example

• Some of discussed Elite capabilities are demonstrated in the

following example

• The example consists of a complex process sequence in order to

show that ATHENA allows to easy transition from in wafer to topography processes and back

• Demonstration is focused on Elite/SSuprem4 interface and on

gridding issues

Elite

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Complex Trench Formation Example (con’t)

• First, an oxide/nitride/oxide stack is formed by oxidation and

conformal deposition

• Then the stack is patterned using simplified mask process

(see figure on page 17)

• After that a nitride spacer is formed by combination of
• conformal deposition and etch-back using RIE

(see figure on page 18)

• ISOTROP and DIRECT parameters are used to control shape and

width of the spacer

Elite

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Patterned Structure

• Stack is patterned using

simplified mask process

Elite

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Spacer Structure

• Nitride spacer is formed by

combination of conformal deposition and etch-back using RIE

Elite

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Complex Trench Formation Example (con’t)

• The thick spacer is used to reduce length of LOCOS with short

Bird’s Beak

• Viscous stress-dependent oxidation gives accurate LOCOS
• (see Figure on page 22)
• The grown LOCOS serves as a mask for subsequent Trench

etching

• So far a very coarse grid in substrate was used. This saved a lot
• f simulation time.
• Much finer grid is needed for trench formation and doping. This is

achieved by DevEdit remeshing (see Figure on page 21)

Elite

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LOCOS Structure

• Viscous stress-dependent
• xidation gives accurate

LOCOS

Elite

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Grid After DevEdit

• Much finer grid is needed for

trench formation and doping

Elite

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Complex Trench Formation Example (con’t)

• Next step opens a window for subsequent trench etching
• It uses a selective nitride etching simulated by RIE model with

high directional etch rate for nitride (see Figure on page 23)

• Deep trench is formed using high directional component of silicon

etch rate (see Figure on page 24)

• Tuning of the trench shape could be done by varying isotropic rate

Elite

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After Selecting Etching of Nitride Plug

• Much Selective nitride etching

simulated by RIE model with high directional etch rate for nitride

Elite

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Structure After Trench Etching

• Much Deep trench is

formed using high directional component of silicon etch rate

Elite

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Complex Trench Formation Example (con’t)

• Next step is to dope walls and bottom of the trench
• It is done by CVD deposition of phosphorus doped poly-layer and

subsequent diffusion (see Figure on page 26).

• It should be mentioned that substrate is not doped because
• thin oxide layer is left after trench etching
• Then polysilicon is etched completely (see Figure on page 27)

Elite

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Structure After Trench Doping

• Dope walls and bottom of

the trench by CVD deposition

Elite

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Structure After Polysilicon Removal

• Polysilicon is etched

completely

Elite

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Complex Trench Formation Example (con’t)

• However, some residual polysilicon islands could remain after

etching

• Slight reoxidation is used to consume these residuals (See Figure
• n page 28)
• After that the trench is filled using oxide CVD deposition

residuals (See Figure on page 28)

• A void could be formed in the process. Next release of
• ATHENA will predict formation of such voids

Elite

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Structure After Trench Reoxidation

• Slight reoxidation is used to

consume residual polysilicon

Elite

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Structure After Trench Filling

• Trench is filled using oxide

CVD deposition

Elite

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Complex Trench Formation Example (con’t)

• After the trench is filled the outer oxide surface is always non-

planar

• There are several methods of surface planarization
• One of them is viscous reflow which removes the step formed

previously (see Figure on page 32)

• Impurity redistribution takes place simultaneously with reflow
• The final step of the process etches all excessive material layers

and leaves only filled trench (see Figure on page 32)

Elite

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Structure After Oxide Reflow

• The final step etches all

excessive material layers

Elite

Structure After Final Planarization

• The final step etches all

excessive material layers

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Elite

Conclusion

• Elite is seamlessly integrated within the ATHENA framework with

SSuprem4 and Optolith

• Elite allows simulation of a wide variety of deposition and etching

processes as well as material reflow and CMP characterization

• Allows to analyze individual process steps and couples multilevel

interconnect structure formation

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