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VLSI Mask Optimization: From Shallow To Deep Learning

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VLSI Mask Optimization: From Shallow To Deep Learning Haoyu Yang 1 , Wei Zhong 2 , Yuzhe Ma 1 , Hao Geng 1 , Ran Chen 1 , Wanli Chen 1 , Bei Yu 1 1 The Chinese University of Hong Kong 2 Dalian University of Technology 1 / 22
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Page 1: VLSI Mask Optimization: From Shallow To Deep Learning

VLSI Mask Optimization:From Shallow To Deep Learning

Haoyu Yang1, Wei Zhong2, Yuzhe Ma1, Hao Geng1,Ran Chen1, Wanli Chen1, Bei Yu1

1The Chinese University of Hong Kong2Dalian University of Technology

1 / 22

Page 2: VLSI Mask Optimization: From Shallow To Deep Learning

Moore’s Law to Extreme Scaling

1940 1950 1960 1970 1980 1990 2000 2010 2020

10,000,000,000

110

1001,000

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A7

A10 A11

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Intel MicroprocessorsApple Microprocessors

2 / 22

Page 3: VLSI Mask Optimization: From Shallow To Deep Learning

Challenge 1: Failure (Hotspot) Detection

Pre-OPC Layout Post-OPC Mask Hotspot on Wafer

I RET: OPC, SRAF, MPLI Still hotspot: low fidelity patternsI Simulations: extremely CPU intensive

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3 / 22

Page 4: VLSI Mask Optimization: From Shallow To Deep Learning

Challenge 2: Optical Proximity Correction (OPC)

Design target Mask Wafer

without OPC

with OPC

4 / 22

Page 5: VLSI Mask Optimization: From Shallow To Deep Learning

Why Deep Learning?I Feature Crafting v.s. Feature Learning

Although prior knowledge is considered during manually feature design, informationloss is inevitable.Feature learned from mass dataset is more reliable.

I ScalabilityWith shrinking down circuit feature size, mask layout becomes more complicated.Deep learning has the potential to handle ultra-large-scale instances while traditionalmachine learning may suffer from performance degradation.

I Mature Libraries

5 / 22

Page 6: VLSI Mask Optimization: From Shallow To Deep Learning

Outline

Hotspot Detection via Machine Learning

OPC via Machine Learning

Heterogeneous OPC

6 / 22

Page 7: VLSI Mask Optimization: From Shallow To Deep Learning

Outline

Hotspot Detection via Machine Learning

OPC via Machine Learning

Heterogeneous OPC

7 / 22

Page 8: VLSI Mask Optimization: From Shallow To Deep Learning

Hotspot Detection Hierarchy

Increasing verificationaccuracy

Sampling

Hotspot Detection

Lithography Simulation

(Relative) CPU runtime at each level

I Sampling (DRC Checking):scan and rule check each region

I Hotspot Detection:verify the sampled regions and report potential hotspots

I Lithography Simulation:final verification on the reported hotspots

7 / 22

Page 9: VLSI Mask Optimization: From Shallow To Deep Learning

Early Study of DNN-based Hotspot Detector∗

I Total 21 layers with 13 convolution layers and 5 pooling layers.I A ReLU is applied after each convolution layer.

…Hotspot

Non-Hotspot

512x512x4256x256x4

256x256x8

128x128x16128x128x8

64x64x16 64x64x3232x32x32 32x32x32

16x16x32

2048

512

C1

P1 C2-1C2-2 C2-3

P2 C3-1 C3-2 C4-1P3C3-3 C4-2 C4-3

C5-1 C5-2 C5-3P4 P5

∗Haoyu Yang, Luyang Luo, et al. (2017). “Imbalance aware lithography hotspot detection: a deep learningapproach”. In: JM3 16.3, p. 033504.

8 / 22

Page 10: VLSI Mask Optimization: From Shallow To Deep Learning

What Does Deep Learning Learn?

Origin Pool1 Pool2

Pool3 Pool4 Pool5

9 / 22

Page 11: VLSI Mask Optimization: From Shallow To Deep Learning

The Biased Learning Algorithm [DAC’17]†

Training Set

Update ε

yh=[0,1]

yn=[1-ε, ε]

MGD:

end-to-end

training

Stop Criteria

Trained Model

Yes

No

80 82 84 86 88 902,000

3,000

4,000

Accuracy (%)Fa

lseAlarm

Shift-Boundary Bias

†Haoyu Yang, Jing Su, et al. (2017). “Layout Hotspot Detection with Feature Tensor Generation and DeepBiased Learning”. In: Proc. DAC, 62:1–62:6.10 / 22

Page 12: VLSI Mask Optimization: From Shallow To Deep Learning

Optimizing AUC [ASPDAC’19]‡

The AUC objective:LΦ(f ) = 1

N+N−

∑N+

i=1∑N−

j=1 Φ(

f(x+

i)− f

(x−j))

.

Approximation candidates:

PSL ΦPSL(z) = (1− z)2

PHL ΦPHL(z) = max(1− z, 0)

PLL ΦPLL(z) = log(1 + exp(−βz))

R ΦR∗(z) =

{−(z− γ)p, if z > γ0, otherwise

‡Wei Ye et al. (2019). “LithoROC: lithography hotspot detection with explicit ROC optimization”. In:Proc. ASPDAC, pp. 292–298.

11 / 22

Page 13: VLSI Mask Optimization: From Shallow To Deep Learning

Conventional Clip based Solution

Region

Conventional Hotspot Detector

Hotspot

Non-Hotspot

Clips

I A binary classification problem.I Scan over whole region.I Single stage detector.

I Scanning is time consuming and single stage is not robust to false alarm.

12 / 22

Page 14: VLSI Mask Optimization: From Shallow To Deep Learning

Region based approach [DAC’19]

Region

Hotspot Core

Region-based Hotspot Detector

Feature Extraction

Clip Proposal Network

Refinement

I Learning what and where is hotspot at same time.I Classification Problem -> Classification & Regression Problem.

Ran Chen et al. (2019). “Faster Region-based Hotspot Detection”. In: Proc. DAC, 146:1–146:6.13 / 22

Page 15: VLSI Mask Optimization: From Shallow To Deep Learning

Outline

Hotspot Detection via Machine Learning

OPC via Machine Learning

Heterogeneous OPC

14 / 22

Page 16: VLSI Mask Optimization: From Shallow To Deep Learning

OPC Previous Work

Classic OPCI Model/Rule-based OPC

[Cobb+,SPIE’02][Kuang+,DATE’15][Awad+,DAC’16][Su+,ICCAD’16]1. Fragmentation of shape edges;2. Move fragments for better printability.

I Inverse Lithography[Pang+,SPIE’05][Gao+,DAC’14][Poonawala+,TIP’07][Ma+,ICCAD’17]1. Efficient model that maps mask to

aerial image;2. Continuously update mask through

descending the gradient of contourerror.

Machine Learning OPC[Matsunawa+,JM3’16][Choi+,SPIE’16][Xu+,ISPD’16][Shim+,APCCAS’16]

1. Edge fragmentation;2. Feature extraction;3. Model training.

14 / 22

Page 17: VLSI Mask Optimization: From Shallow To Deep Learning

Machine Learning-based SRAF InsertionSRAF Insertion with Machine Learning [ISPD’16]¶

Label: 1

Label: 0

0 1 2N%1sub%sampling0point

Tackling Robustness with Dictionary Learning [ASPDAC’19]‖

n+

s+

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¶Xiaoqing Xu et al. (2016). “A machine learning based framework for sub-resolution assist featuregeneration”. In: Proc. ISPD, pp. 161–168.

‖Hao Geng et al. (2019). “SRAF Insertion via Supervised Dictionary Learning”. In: Proc. ASPDAC,pp. 406–411.

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Page 18: VLSI Mask Optimization: From Shallow To Deep Learning

Machine Learning Assists Model-based OPC [ASPDAC’19]∗∗

I Replace lithography simulation (slow) with machine learning-based EPE predictor(fast) in OPC iterations.

∗∗Bentian Jiang et al. (2019). “A fast machine learning-based mask printability predictor for OPCacceleration”. In: Proc. ASPDAC, pp. 412–419.

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Page 19: VLSI Mask Optimization: From Shallow To Deep Learning

GAN-OPC [DAC’18]††

0.2 0.8

BadMask

GoodMask

Discrim

inator

Generator

EncoderD

ecoder

Target

Mask

Target & Mask

I Better starting points for legacy OPC engine and reduce iteration count.††Haoyu Yang, Shuhe Li, et al. (2018). “GAN-OPC: Mask Optimization with Lithography-guided Generative

Adversarial Nets”. In: Proc. DAC, 131:1–131:6.17 / 22

Page 20: VLSI Mask Optimization: From Shallow To Deep Learning

Outline

Hotspot Detection via Machine Learning

OPC via Machine Learning

Heterogeneous OPC

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Page 21: VLSI Mask Optimization: From Shallow To Deep Learning

An Observation of Previous OPC SolutionsMachine learning solutions rely on legacy OPC engines

Generator RealFake

Generator

(a)

(b)

Feed-forward Back-propagetion

Discriminator

Litho-Simulator

Legacy OPC engines exhibit different performance on different designs

1 2 3 4 5 6 7 8 9 1002468·104

Design ID

MSE

MB-OPCILT

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Page 22: VLSI Mask Optimization: From Shallow To Deep Learning

A Design of Heterogeneous OPC Framework

Classification Model

ILT

MB-OPC

Mask

MaskDesignDesigns

OPC-1

OPC-N

Masks

Masks

… …

We design a classification model that can determine the best OPC engine for a givendesign at trivial cost.

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Page 23: VLSI Mask Optimization: From Shallow To Deep Learning

Training on Artificial DesignsI Training data comes from GAN-OPC and is labeled according to results of MB-OPC

and ILT.I Test on 10 designs from ICCAD 2013 CAD Contest.

0 20 40 60 80 1000.00

20.00

40.00

60.00

80.00

100.00

Epoch

Accuracy

(%)

Training Testing

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Page 24: VLSI Mask Optimization: From Shallow To Deep Learning

Experimental Results

1 2 3 4 5 6 7 8 9 100

2

4

6

8·104

Design ID

MSE

MB-OPCILT

HOPC

Several BenefitsI Does not require extremely high prediction accuracy of the classification model.I Take advantages of different OPC solutions on different designs.

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Page 25: VLSI Mask Optimization: From Shallow To Deep Learning

Conclusion and Discussion

So Far:I Recent progress of deterministic machine learning model for hotspot detectionI State-of-the-art machine learning solutions for OPC and SRAF insertionI A heterogeneous OPC framework guided by a classification engine

Future:I Manufacturability issues.I Classification challenge when more than two OPC engines are available.

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