New Color Alignment for CMOS Image Sensor

Transcription

1 New Color Alignment for CMOS Image Sensor TOWER: Miri Kish Dagan, Hadas Rechtman, Oshri Moshe ASML: Remi Edart, Yehuda Kanfi, Patrick Warnaar, Richard van Haren

2 Content Introduction Requirement Technical Background Simulation Alignment & Overlay Results Conclusions

3 Introduction PAS5500/450F Multiple consumer & professional applications with Image Sensor In volume production Productivity is more and more critical It requires improved alignment solutions TWINSCAN XT:400F

4 Introduction Alignment Choices Traditional strategy Enhanced strategy More productivity and real estate TTL Zero Layer Athena Non-Zero Mark -1 +1

5 Content Introduction Requirement Technical Background Simulation Alignment & Overlay Results Conclusions

6 Requirement - Absorption of Alignment Signal Green Alignment Transmittance [%] Blue Color Resist Wavelength [nm] Red Alignment Red Color Resist Green Color Resist Production environment requires robust wafer alignment enabled with strong enough alignment signal

7 Content Introduction Requirement Technical Background Simulation Alignment & Overlay Results Conclusions

8 ATHENA Dynamic Range Alignment Repeatability [nm] Green - X Red - X Green - Y Red - Y Alignment Signal Strength (8.0um grating) - WQ [%] Highly repeatable down to at least 0.03%

9 Versatile Scribelane Primary Mark (VSPM) VSPM-AH VSPM-AA157 AA5 AH53 16-µm period: First order 3.2-µm period: Fifth order Enhanced theoretical signal strength

10 Metal Plateau I alignment φ sin 2 ( ) 2 with φ = 2π (2nd) λ Blue Resist Passivation Metal Last Via Last Metal Last -1 Via Last -1 Metal Last -2 d d Via Last -2 I ML-1 I ML-1 I ML-2 I ML-2 High probability to have strong enough alignment signal intensity

11 Mark Implementation Planarization Micro lens Planarization Color resist clear out Green / Red / Blue Planarization Passivation Metal Last VSPM AA157 ML SPM AH53 ML Via Last SPM AH53 VL Metal 3 Via 3 SPM AH53 Metal 2 Via2 SPM AH53 Metal 1 Contact SPM AH53 Location Color resist layers are part of the device layer stack

12 Content Introduction Requirement Technical Background Simulation Alignment & Overlay Results Conclusions

13 Fourier-Transform-based Simulation Signal absorption with thicker color resist Signal variation - f(sin x) - with film stack interferences Alignment Signal Strength ML-1 Red ML-2 Red Normal operating range ML-1 Green ML-2 Green Blue Color Resist thickness [nm]

14 Simulation Influence of Oxide thickness Alignment Signal Strength ML-1 Red ML-1 Green ML-2 Red ML-2 Green Mark implementation with higher signal is layer-stack dependent Different Via Last Oxide thickness ML-1 Red ML-2 Red ML-1 Green ML-2 Green Blue Color Resist thickness [nm] Optimum implementation switches from ML-2 to ML-1 Therefore CMP variation leads to more alignment robustness

15 Simulation No Green signal absorption with Green color resist At least one implementation with enough signal Alignment Signal Strength ML-1 Red ML-1 Green ML-2 Red ML-2 Green Green Color Resist thickness [nm]

16 Simulation No Red signal absorption with Red color resist At least one implementation with enough signal Alignment Signal Strength ML-1 Red ML-2 Red ML-1 Green ML-2 Green Red Color Resist thickness [nm]

17 Content Introduction Requirement Technical Background Simulation Align. & Overlay Results Conclusions Image Sensor pixels

18 Mark Implementation Planarization Micro lens Planarization Green / Red / Blue Planarization AH53 VL AA157 ML AH53 ML Passivation Metal Last VSPM AA157 ML SPM AH53 ML Via Last SPM AH53 VL Metal 3 Via 3 SPM AH53 Metal 2 Via2 SPM AH53 Metal 1 Contact SPM AH53 Location One Metal Plateau in Metal Last -2

19 Experimental Data Wafer Plot Measurement Scheme 30 nm Mark on-line measurement Alignment Signal Strength (WQ) Overlay off-line measurement Max overlay per wafer and field

20 Positioning Alignment Signal Strength Alignment Signal Strength Metal Last AH53 VL AH53 ML AA157 ML

21 Positioning Alignment Signal Strength Alignment Signal Strength [%] Metal Last AH53 ML AH53 VL Green Resist AA157 ML Red Resist Blue Resist AH53 ML AH53 VL AA157 ML

22 Capturing Alignment Signal Strength Alignment Signal Strength [%] Metal Last AH53 ML AH53 VL Green Resist AA157 ML Red Resist Blue Resist AH53 ML AH53 VL AA157 ML

23 Max Overlay per Wafer Processes Alignment Measurement Machine Blue B - /400 Red B - /400 Green B - /400 Planarization /400 Passivation /400 Metal Last A - /400 VSPM AA157 Off-line target ref. Aligning to 2 VSPM AA157 pairs to enable maximum throughput Max X per wafer [nm] GREEN RED BLUE Raw Multiple Machine Product Max Overlay per wafer, per Color layer using PAS5500/400 with optimized Process Corrections Max Y per wafer [nm] GREEN RED BLUE

24 Max Overlay per Field # Field Field Perf. Rate [%] 120% 100% 80% 60% 40% 20% 0% Max Overlay [nm] 70 X Y X Y X or Y Usual specifications range Overlay Requirements [nm] Raw Max Product Overlay per field (20 wafers, 7 fields) for all Color layers

25 Content Introduction Requirement Technical Background Simulation Alignment & Overlay Results Conclusions

26 Conclusions Simulation & experimental results show Color layers easily aligned With appropriate dual marks in Metal Last High throughput-driven alignment strategy Meeting product overlay performance for Image Sensor Machine configuration ultimately determines product overlay performance

27 ASML robustly aligns Color layers with high throughput