IMPACT Internal Document for Summary IMPACT...

Summary

IMPACT RoundtableLithography + DfM

IMPACT Internal Document for IMPACT Participants Only

Dialog on industry challenges and university research activities among technologists from

Participating Companies, Students and Faculty

Held at SanDisk, MilpitasSeptember 24, 2008

For further dialog contact the IMPACT faculty: Puneet Gupta, Andrew Kahng, Andy Neureuther,

Kameshwar Poolla, Costas Spanos

109/24/2008University of California • Berkeley • San Diego • Los Angeles

IMPACT • Lithography/DfM • Roundtable 2 09/24/2008

IMPACT UC Discovery Industry Team –Thanks!

University of California • Berkeley • San Diego • Los Angeles

http://www.cmg.org/measureit/issues/mit41/m_41_2/ibm_logo.gif

http://www.xilinx.com/

http://images.google.com/imgres?imgurl=http://itreview.belproject.com/media/1/20060227-sandisk-logo.jpg&imgrefurl=http://itreview.belproject.com/%3Fquery%3DSD%2Bcard%26amount%3D0%26blogid%3D1&h=70&w=252&sz=15&tbnid=8z8nAvNX-bTd3M:&tbnh=31&tbnw=111&prev=/images%3Fq%3Dsandisk%2Blogo%26um%3D1&start=2&sa=X&oi=images&ct=image&cd=2


Roundtable Approach

Objective: guide research in the IMPACT program understand litho & DfM challenges in industryunderstand research capabilities in universitieswhat are issues that are relevant and timely to industry and academic in nature

Format:2 hours of presentations (8 industry, 5 faculty)– Summarized by speaker suggestions

2 hours of dialog 45 participants (30 ind.15 univ.)– Summarized by topics (DfM, Variability, Physics)


SpeakersIndustry

Lars Liebmann, IBM, ASICChandu Gorla, Flash Memory, San Disk Vivek Singh, Microprocessors, IntelZhenhai Zhu, Double Patterning, CadenceHuixiong Dai, thin-films for pattern transfer, AMATMamoru Miyawaki, Exposure tools, CanonBob Socha, Exposure tools, ASML Stan Stokowski, Inspection, KLA-T

University of CaliforniaAndrew Kahng, UCSDDfM toolsPuneet Gupta, UCLADfM toolsKameshwar Poolla, UCB AlgorithmsCostas Spanos, UCB variability and assignment of causesAndy Neureuther, UCB fast-CAD, electrical test, EM


Main Points

DfM is all about knowing how much performance to leave on the table to make the IC manufacturable.

– DfM (or computational Lith., etc.) is expected to provide a full generation now that lithography is no longer scaling.

– DfM is time-changing as DfM results acted on in the fab improve the process but design requires models extrapolated to the future improvement at tapeout date.

DfM helps manage complexity– Support playing what-if games at macro or product level– Need to make tolerance consequences and budgets visible– Scaling layouts to the next generation no longer works - requires design

Double patterning technology is nearly here for the 22nm node (logic and flash) and 32nm node (memory) as a necessary reality.

– The choice of DP method depends on product and tolerances including overlay– DP methods require rethinking layout concepts and metal layers in design– Thick mask EM effects must be mitigated– Need better models of all physical processes including 3D effects– Simulated assisted metrology is required


Lars Liebmann, IBMChallenge: DfM needs to reflect the improvement of process with time.

Once actionable, modeled, systematic sources of variation are found through statistical methods (of DfM) they may be corrected in either Fab or Design. What the designer wants is not a current but a future model of process maturity at the tapeout date for their product.

Research Suggestions: (Some of these are detailed in later slides)Process Variation Analysis, Decomposition, and Correlationthat would facilitate more focused process or layout optimizationMore Rigorous Approximation to Mask EMF Effects including high-NA and parallelized codesExtension of fast first principle predictive modeling solutions to etch, CMP, implant, annealSimulation Assisted Metrology for understanding inspection and improving extraction of meaningful metricsMechanical Models for Long Range Stress Effects


Chandu Gorla, SanDisk

Challenge: In Flash memory generations are only 12 months apartImmersion is in production, spacer pattern doubling is nearly here, and EUV and Imprint are just around the corner

Suggestions:Materials for double patterning: freeze or multiple exposure; single layer double exposureOverlayOdd and even pattern dependence: understanding and modeling the interaction between litho and etchDfM needs to be flexible to include novel integration schemes and their tolerancesEUV and Imprint need study


Vivek Singh, Intel

Comment: The following suggestions emphasize modeling and algorithms. Topics that are theoretical are easy to transfer quickly to industry.

Suggestions:Recovering the lost 3rd dimension (resist thickness and mask edge effects). Litho effects lost in the popularity of OPC with only 2D effectsMask scattering to include ‘thick-mask’ effects at advanced nodesInverse Lithography that is fast and not too fragmentedOptimization algorithms that are fast for sizeable numbers of discrete variablesLitho/Etch coupled models with innovation in fast formulations for the complex physics of etch.


Zenhai Zhu, Cadence

Challenge: Splitting a layout for double patterning is not just a tapeout problemScaling often requires going back into the design for contacts, redundant vias, etcRestricted Design Rules are often ridiculously restricting

Suggestions:Automated netlist to physical layoutSingle-contact process (Reliable litho, deposition, electroplating of small holes)


Huixiong Dai, Applied

Challenge: Double patterning is the only feasible solution for 32nm HP and beyond before 2012.Meeting NAND Spec (+/-10%) for 32nm and 29nm Half-Pitch26nm and 22nm is limited by resist LWR

Suggestions:Sidewall Spacer Double Patterning with non-gridded Design requires Design Evolution for LogicHighly regular gridded designs are promising for 44 nm pitch but a greater patterning concern is the isolated slots Resist LWR is an industry wide challenge and it interplays with the core and space tolerances


Mamoru Miyawaki, Canon

Challenge: Future nodes such as 22 nm require very careful examination of techniques and tolerance budgets.

Suggestions:Verification methodology to reproduce the actual experimental data by DfM software. (How many parameters? Accuracy for each?)DFM provide a system for understand every aspect of the whole process and error budgetsMethods for monitoring very low lens aberrations and assuring that aberrations have virtually zero effect on lithography.


Bob Socha, ASML

Challenge: DPT for the 22nm node (logic) and 32nm node (memory) is a necessary reality

Suggestions:Overlay is critical in double patterning and in vertical scaling(3D layout)Illumination source and Mask Optimization needs to interact with designers, fab, and scanner vendorHow can this interaction knowledge be included in the design library and in the place and route CAD tools


Stan Stokowski, K-T

Challenge: It is not just a matter of seeing the variation but rather how this information can be used to optimize all of the settings

Suggestions:Understand IC process control on a broader basis and determine what to measure and inspect for controlling the processLithography simulation of mask 3D effects at the waferIdentify issues in EUV in advanceIdentify issues in Imprint in advance


DFM Wishlist Discussion 1 (Gupta, Kahng)#1. Accurate, quick map from design rules to product quality (area, power, frequency, yield, (COO)) (Rob Aitken, ARM)

– need an infrastructure within which to play such what-if games at macro or product level (Lars Liebmann)

– Framed by SPICE/ITRS parameters, or TCAD, or process knobs?– physical parameters (Lg) preferred to electrical (Vt) for informing process (Vivek Singh, Lars Liebmann)

#2. New ways for design to ease required process control capability (Zhilong Rao, AMAT)#3. Design flow integration of systematic variation models

– Orthogonality of designs to systematic variations (related to above #1, #2)– + Metrology to support

– But, aren’t big systematic issues solved in the fab? (Lars Liebmann)random variations increasing in significance (JL de Jong, Xilinx)

– Wafer-level systematic variation is less well-addressed than die/field-level where OPC, PPC have had success (Costas Spanos)

#4. Research on DPL ‘bimodal’ problem– Xilinx: already study mismatch; assume have to extend to DPL context– ASML / Socha: feel this is valuable work; make sure to cover overlay as well as CD

– DPL flavor: bimodal distribution of space, vs. bimodal distribution of width– IBM (Lars): bimodal problem is unacceptable, and hence uninterested in this process if such a

problem exists(!) assume that this is controlled– Interconnects also of interest (Lars); ongoing at UCLA, UT, …– N.B.: even if distributions perfectly matched, still lose spatial correlation– Solving a single-layer formulation may be irrelevant ! (Apo, Cadence)– University solvers: transferability of code is of interest (IBM, ASML, ...)


DFM Wish list Discussion 2 (Gupta, Kahng)#5. Layout automation for fixed pitch / fixed orientation (JL de Jong, Xilinx)

– May be beyond capabilities of university research? (Lars)– But, prototypes of new ideas possible? (Andy)– IMPACT can at least help industry make a decision– Cf. Rob Aitken wishlist #1

#6. Miyawaki-san (Canon) comment: How do I determine my budget out of a “DFM” tool?

– Issue today: electrical budgets not necessarily well-aligned to process budgets– Cf. LEE rule / taper shape / leakage-area correlation of metrics – UCLA/UCSD– Can you even establish yield impact of a litho hotspot? (Lars)– Can you tell me the exact yield impact of double-cut vs. single-cut vias? (Lars)

– (Berkeley work (Spanos, Poolla) is responsive to these types of questions...)#7. (Huixiong Dai, AMAT) Have you looked at layout that is specifically directed at spacer double-patterning?

– UCLA is starting to look at this a bit (e.g., M1 patterning) – maybe some insights within a few months

General comments– Time horizon?– Tractability to students?– Nature of application/specific research: artifactual, less generalizable or impactful than a

new framework or theory? (Vivek)– Ultimately, DFM tools must become more integrated into overall process planning and

budgeting (Andy)


Metrology and Algorithms Wish list Discussion 3 (Poolla and Spanos)

#1 Uncertainty in Circuit SimulationIs there a need to go beyond the 4 corner model of spread in performance? (Yes)Is there a need to propagate uncertainty through models that are nonlinear (max)?How are results of uncertainty characterization reinserted into design flow?

Does not matter as both design and process have limitations. This is parametric loss

Understanding robustness to estimation errors.#2 Accuracy of Circuit modelingAre all the models under zero variability conditions that go into tool sufficiently

accurate to be predictive of circuit performance.SPICE 15% to 20% (but derivative is more accurate.)Voltage and temp may dominate corner speed estimates more than processDesigners might choose devices with low variability (fixed pitch price) this needs to be included in Circuit simulation options in SPICE) Tool to help make a decision before a layout exists. Interaction between design models and layout and need to include and quantify other factors such as temp.Corners assume convex hull but possibility that worst situation may be in the middle (temp).


Metrology and Algorithms Wish list Discussion 4 (Poolla and Spanos)

#3 What is DfM?DfM is all about how much you leave on the table to make it manufacturable and knowing how much that is.Looking for us to estimate the performance benefit of the best possible variation reduction. (How much faster would the circuit run?)Alternatively to modeling uncertainty DfM is about reducing variation and could use the 5 tools described.If wavelength gap had not increase would we have had a need for DfM? How much is Litho Today?

#4 DfM ScopeDoes place and route use models? Real data driven used upstream in design?Need layout checked afterward. Monte Carlo is slow is there sampling ways to speed it up.

#5 Roles for DfMAt 90 nm processes are well characterized yet full process aware design might result to the improvement of a full generation.The next generation plans to get the realizable speed extrapolation from the previous generation but process discontinuities (metal or new foundry) require a new guess.

– This is a challenge for data driven modeling. – A solution is to keep layout and recalibrate on 10% structures, group and see effects, and focus on possible

causes at length scale.– Apply machine learning to translate existing (SEMs) to changes in process

Litho Wish list Wish list Discussion 5 (Neureuther)


#1 Sources of Variation:Methods for identifying variations due to illumination in addition to focus and dose Masks: More Rigorous Approximation to EMF EffectsOverlay and propagation in 3DMethods for aberration measurements and assurance of zero contribution to patterning

#2 Process ModelingExtension of Process Modeling{Litho 3D, Fast Image {ideas from other fields}, Etch, Anneal, CMP}Mechanical Models for Long Range Stress Effects on wafer distortionSimulation Assisted Metrology

– CD SEM is uncaligbrated compared to artifact (10 nm uncertainty)– 3rd Dimension is lost here as well

#3 FutureProcess {equivalent of negative resist?}Look ahead to understand issues in EUV and IMPRINT3D Integration

– Double patterning (reach through, CMP, resistance of contact both yield and circuit performance)– Some work on stacking but not being pursued yet– Fixed pitch small circuits study on how well work and how much leave on table (EDA Ind)– Need automatic tool to relate to 3D configuration (EDA ind)


Liebmann: Process Variation Analysis, Decomposition, and Correlation

Given sets of empirical data taken across multiple lots, wafers,chips, and field locations, collected after various process steps (e..g. resist, etch, anneal) by various means (e.g. sem, electrical) – establish frequency, process, and layout correlations that would facilitate more focused process or layout optimization. The goal would be to develop an analysis and visualization software platform that combines layout information, process simulations over different length scales, and data analysis to pinpoint error sources. Detailed understanding of correlation distances may also improve incremental layout optimization (e.g. cell-level, macro-level, chip-level).

Liebmann: More Rigorous Approximation to EMF Effects


Need sufficiently accurate EMF calculations to incorporate into iterative optimizations. Accuracy of domain decomposition is being questioned at ultra-high NA and extreme illumination angles. Code should focus on extreme parallelization, potentially running on supercomputing systems such as CCNI. Also, need to make Tempest 7.0 available.

Liebmann: Extension of Process Modeling


Build fast first principle modeling solutions for processes other than lithography (e.g. etch, cmp, implant, anneal). Models should be physical enough to allow accurate predictive modeling.

Liebmann: Simulation Assisted Metrology


Build models to gain first principle understanding of metrology image collection and data extraction to improve accuracy against meaningful metrics (e.g. top-width, bottom-width, sidewall angle).


IMPACT Lithography/DfM Roundtable

Thanks to AllSpeakers for preparing commentsTechnologists for your comments and

interactionsStudents for doing the hard work !SanDisk for hosting and Starleigh Arce

for local arrangementsChangrui Yin for web site posting and

reservations

Reminder: IMPACT Workshop, Wed. October 29th at the AMD Commons Building, Santa Clara

IMPACT Internal Document for Summary IMPACT...

Documents

Transcript of IMPACT Internal Document for Summary IMPACT...