Application of Autom ated Design Migration to Alternating Phase - - PowerPoint PPT Presentation

Application of Autom ated Design Migration to Alternating Phase Shift Mask (AltPSM) Design Fook-Luen Heng Jennifer Lund IBM T.J. Watson Research Center Lars Liebm ann IBM Microelectronics ISPD 2001

Outline

Background Prior art in altPSM legalization Our approach Results Future challenges

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AltPSM Prim er

Powerful Resolution Enhancem ent Technique (RET) Uses destructive interference of projecting light

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Phase shapes need to be created for critical elem ents They need to satisfy the phase transition requirem ent

Traditional COG mask AltPSM mask cross sect ion chrome glass

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polysilicon shapes

Background

Layout Data

Custom Library Array Core

Assembly Verification Extraction

OPC SRAF AltPSM

RET Data

Tape Out

Layout Im pacts Density im pacts: up to 6% (180nm node) Resource im pacts: 10-20% Verification, phase shapes generation AltPSM legalization and m igration Assem bly m ethodologies

Mask Data

Conflicts in AltPSM Layouts

Forbidden Topologies

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T-junction Odd-even run

Spacing conflict

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Resolving AltPSM Conflicts

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Com paction Legalizes a layout topology Minim ize: xi Subject to: xi - xj m d ij Translate sym bolic layout to physical layout Mim im um Perturbation Legalizes an alm ost correct layout Minim ize: w i * || xi - xiold || Subject to: xi - xj m d ij Migrate existing layouts from source to target technology

Prior Art in Layout Legalization

Xi Xj Xi Xj

Xj - Xi m d ij d ij

Prior Art in Layout Legalization

Compact ed layout Minimally pert urbed layout

Constraint based Adjacent relationship between objects does not capture altPSM requirem ents

DI FF- CA Spacing violation Spacing and width get squeezed to minimum Non- minimum spacing and width are preserved

Conflict De te ction & Le galization

PSM Verification (Galan et al) Geom etric m ethod based on counting ends Legalization based on design guidelines Exceptions are allowed in waivered layouts Graph Bipartizations (Kahng et al) Graph theoretic m ethod using a feature grap h Legalization form ulated as a graph bipartization Minim um topological m odification

Geometric method Feature graph shif t er node f eat ure node conf lict node int ersect ion cont aining

• dd number of crit ical

segment ends

Marker Shapes

Derived shapes that denote conflicts Used to suggest legal solutions

line-end conf lict line-end conf lict markers ent ire shape edge is classif ied as crit ical

Marker shapes generation

• 1. Classified critical features
• 2. DRC - including altPSM conflict detection
• 3. Derived m arkers with shape operations

Instructing Minim um Perturbation

WNC: Non-critical width L

NC : Non-critical length

W : Width of PC shape

Marker PC W NC LNC W PC

s L m R m L m T m B s B s T Edges of m arker coincident with PC shape m L, m R, m T, m B denote left, right, top and bottom edges of m arker s L, s T, s B denote left, top and bottom edges of PC

Instructing Minim um Perturbation

X-direction rules Intersection(Marker, PC) mL

NC

Length(Marker) m L

NC

m R - s L m L

NC

m R - m L m L

NC

Y-direction rules OverlapOf(Marker, PC) m W Width(Marker) m WNC

Marker P C Marker P C

m T- s B m W s T- m B m W m T- m B m WNC

marker shif t ed upward marker shif t ed downward

Resolving T-junction Conflict

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In practice, use a sim plified rule to expand all legs

• f T-junction

gat e const raint prevent ed expansion P C dif f usion

Prioritization of Conflict Resolutions

Adjust m inim um perturbation objective function Manipulate layout variables to control changes

• 1. Expand m arker shapes

Freeze non-m arker variables

• 2. Move and/or expand m arker shapes and

critical features without size increase Un-freeze variables of critical features Add source to sink upper bound constraint

• 3. Allow shapes in predeterm ined level to

m ove Un-freeze variables of shapes

• 4. Allow layout to expand by percentage

Expand upper bound constraint

Sum m ary

Sum m ary AltPSM legalization is m ore an art than a science Used m arker shapes to indicate conflicts Designed solutions based on experience Form ulated sol'n as a layout optim ization problem Prioritized solutions based on design preferences

Results

Results Custom ized MASH to perform altPSM legalization Migrated layouts com parable with m anual results Typical standard cell took between 1 and 30 secs A custom m ultiplexer with 50+ devices took < 1 m in Sam e layout took 8 hrs to legalize m anually ! Established a feasibility m ilestone

Exam ple of AltPSM Legalization

Exam ple of AltPSM Legalization

Future Challenges

Constraint generation technique that discovers altPSM requirem ents Autom ation to create altPSM com pliant layouts AltPSM assem bly tools and m ethodologies

Layout Data

Custom Library Array Core

Assembly Verification Extraction OPC SRAF AltPSM

RET Data

Tape Out

Mask Data

Today's standard cells Cells with phase shapes