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

AltPSM Prim er Powerful Resolution Enhancem ent Technique (RET) Uses destructive interference of projecting light polysilicon shapes cross sect ion Traditional COG mask AltPSM mask 180 o 180 o 0 o 0 o 0 o chrome glass Phase shapes need to be created for critical elem ents They need to satisfy the phase transition requirem ent 0 o 180 o 0 o 180 o

Background OPC Custom Tape Library Verification Assembly Layout RET Extraction Out Data Data Array Core SRAF Mask AltPSM Data 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

Conflicts in AltPSM Layouts Forbidden Topologies 0 o ?? 180 o 180 o 0 o 180 o 0 o T-junction Odd-even run Spacing conflict 180 o 180 o 0 o 0 o

Resolving AltPSM Conflicts ??? ??? ???

Prior Art in Layout Legalization Com paction d ij Legalizes a layout topology X i X j Minim ize: � x i X j - X i m d ij Subject to: x i - x j m d ij X i X j Translate sym bolic layout to physical layout Mim im um Perturbation Legalizes an alm ost correct layout Minim ize: w i * || x i - x iold || Subject to: x i - x j m d ij Migrate existing layouts from source to target technology

Prior Art in Layout Legalization Non- minimum DI FF- CA Spacing spacing and width Spacing and width get violation are preserved squeezed to minimum Minimally pert urbed layout Compact ed layout Constraint based Adjacent relationship between objects does not capture altPSM requirem ents

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 shif t er node f eat ure node int ersect ion cont aining odd number of crit ical segment ends conf lict node Geometric method Feature graph 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

Marker Shapes Derived shapes that denote conflicts ent ire shape edge is Used to suggest legal solutions 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 line-end conf lict line-end conf lict markers

Instructing Minim um Perturbation W NC : Non-critical width W NC PC W L NC : Non-critical length W : Width of PC shape L NC m T s T Marker PC s B m B m L s L m R 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 Marker m R - s L m L Intersection(Marker, PC) m L P C NC NC m R - m L m L Length(Marker) m L NC NC Y-direction rules m T - s B m W OverlapOf(Marker, PC) m W Marker s T - m B m W P C Width(Marker) m W NC m T - m B m W NC marker shif t ed upward marker shif t ed downward

Resolving T-junction Conflict ?? 0 o 180 o In practice, use a sim plified rule to expand all legs of T-junction gat e const raint prevent ed expansion dif f usion P C

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 Today's standard cells Cells with phase shapes OPC Custom Tape Library Verification Assembly RET Layout Extraction Out Data Data Array Core SRAF Mask AltPSM Data