Defect management and control. Tsuyoshi Moriya, PhD Senior Manager Tokyo Electron Limited

Transcription

1 Defect management and control Tsuyoshi Moriya, PhD Senior Manager Tokyo Electron Limited

2 Background Case study: A maintainer has good hands Only he achieved good yield for every maintenance But... He could not explain why he improved defectivity better than the other maintainers. His maintenance was checked Only he did wipe up manifold areas of plasma etch tools. But... He could not understand why it is effective... Scientific approach is so important! Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 2

3 Scientific approach Investigate improvement opportunity Mechanism investigation in equipment Cause analysis: Particles, damages Set up hypothesis Methodology of defect control Countermeasure of defects Verify hypothesis Apply and check the effects Provide solutions Expand solutions into the fab Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 3

4 Investigate improvement opportunity Typical defect source of plasma etch tool Molecular contamination Humidity Nucleation Film flake Robot induced particles Suspension Turbo pump Transfer Loadlock Chamber Recoil from turbo pump Abnormal discharge Electric Damage Many causes of defects must be specified in equipment Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 4

5 Analysis of phenomena Standard lighting UV lighting Wet maintenance can be improved by visualizing with use of UV light Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 5

6 To count on-site particles Surface particle detection Before cleaning After cleaning To reveal where is the source of particle contamination We inspected the contamination on the parts Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 6

7 Mechanism investigation Byproduct inside turbo pump Why particles cannot drop between rotating blades? Rotation Particles~1.6m/s Blade~366m/s Fast moving blades hit particles to process chamber Round edge hits almost particles Hitting point (0.1~0.3mm) Recoil Turbo pump Falling particles must be recoiled by rotating blades Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 7

8 Defect Counts Set up hypothesis Many defects and particles were observed near turbo pump Defect level was improved after turbo pump overhaul Particle Map Turbo Pump Overhaul Turbo Pump side Days Hypothesis: Defects are caused by particles from turbo pump called as recoil particles Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 8

9 Typical surface particles Before wet cleaning After wet cleaning T. Moriya et al.: Proc. ISSM2012 Particle on part surface was checked before and after wet cleaning Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 9

10 Particles on lid surface Surface particle detection Particles on the lid surface were counted by surface particle counter (QIII+) Isolation valve motion (open & close) for several times Compare particles between farther and above turbo pump Farther Above Isolation valve 5 0 Farther Above Before open/close After open/close T. Moriya et al.: Proc. ISSM2014 Lid was contaminated only above the turbo pump Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 10

11 Verify hypothesis In-chamber particle monitor Recoil particles were observed in process chamber above turbo pump Beam stopper Wafer 40mm Status signal B.P. Filter (532nm) Camera Laser PC Pulse generator To clarify the defect source, in situ monitor is useful Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 11

12 Defect amount [a.u.] Provide solutions Ceramic fiber fabric is installed at manifold wall Result: Defect count on wafer Manifold Without Fibers T. Moriya et al.: Proc. ISSM2014 Recoil particles were almost eliminated Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 12

13 Recoil particles from turbo pump Root cause of defects were existing near turbo pump area Falling particles must be recoiled into process chamber Defects were reduced by reducing recoil particles in equipment Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 13

14 How particles are eliminated in manufacturing tools? Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 14

15 In-chamber particle observation Analyzing images Showerhead Particles Showerhead A/D Converter Particles I-CCD Camera Wafer Particle Wafer Wafer Wafer YAG Laser λ=532nm Optics Wafer edge T. Moriya et al.: J. Vac. Sci. Technol. A 18, 1282 (2000) Particle behaviors could be specified by using laser light scattering Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 15

16 Particle observation [%] Particle during gate open and gas flow 100 Process chamber Mach Number Calculation (100 mtorr) Transfer chamber ( 400 mtorr) Particle re-suspensions are induced by gas viscosity evaluated Process as (Q chamber m) k v m 0.1 mtorr 14 mtorr 100 mtorr 200 mtorr v r Q m 2 Particles N are n induced n Rby shockwave p Step Ar [sccm] N 2 [sccm] O 2 [sccm] Total [sccm] (Q m) Transfer chamber pressure [mtorr] Particle Yes Yes None Yes Yes None Yes Yes None Yes Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 16

17 Contaminating mechanism Necessary condition Pressure difference exceeds 2x Flow rate x mass number: Increases Shockwave or gas viscous force suspend particles in vacuum chamber We have to focus on the mechanisms rather than the phenomena Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 17

18 Particles during wafer chuck Particle suspension at the timing of wafer chucking Substrate surface Dielectric constant Particle material Dielectric constant Particles Silicon ~11 PTFE ~2 5 or more Silicon ~11 Silica ~4 < 5 Silicon dioxide ~4 PTFE ~2 < 5 Silicon dioxide ~4 Silica ~4 0 Photoresist ~3 PTFE ~2 < 5 Photoresist ~3 Silica ~4 < 5 Anodized aluminum ~9 PTFE ~2 5 or more Anodized aluminum ~9 Silica ~4 < 5 Particle outbreak when dielectric constants are different Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 18

19 Number of particles Particle vs. chucking voltage More particles suspend as voltage is larger Voltage (V) Particle suspension is influenced from voltage Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 19

20 Particles by Maxwell stress Particles on wall surface Particle suspends Because of particle, by Maxwell stress electric field is distorted Electric field is stabilized Maxwell stress Chucking Voltage ON OFF Particles contaminate wafer on chucking wafer Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 20

21 Contaminating mechanism Necessary condition Particle and wall differ in dielectric constant Wafer chucking voltage supplied Maxwell stress suspends particles f ρe 1 2 E 2 ε 1 2 dε E 2 d ρ: Charge E: Electric strength ε: Dielectric constant τ: Density Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 21

22 ISPM Count Particles on wafer [>0.09µ m] Make pressure work for you Typical pump and purge cycles just stir particles Proposed method Pump/Purge Proposed N 2 Purge Purge port Pump/Purge Cycles ISPM Wafer Proposed methodology Particles leave float Stage Vacuum Line This sequence suspends particles off walls and carry them into the pump line Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 22

23 Special purge method Pump-line particle monitor Particle motion during cleaning sequence Process Chamber wafer Pump Line In situ particle monitor within pump line To dry pump This sequence suspends particles off walls and carry them into the pump line Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 23

24 2005/5/4 17: /6/3 10: /6/9 15: /6/26 14: /7/4 18: /7/23 0: /8/3 0: /8/12 10: /8/23 8: /8/31 20: /9/10 19: /9/18 13: /9/28 13: /10/6 18: /11/11 19: /12/13 14: /12/27 4: /1/9 23: /1/18 17: /1/31 14: /2/15 18: /2/28 17: /3/12 3: /3/19 22: /3/28 5: /4/4 19: /4/13 6: /4/25 19: /5/5 23: /5/30 1:26 Normalized final yield Particle level (a.u.) Typical result Conventional Experiment Under countermeasure Yield improved Low yield High particles Low particles Final yield Particle (>0.2 痠 ) Particle (>2.0 痠 ) 0 Date Particle reduced and yield improved (~7%) Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 24

25 Defect management and control Fab Level High-level knowledge and suitable tool for defect improvement Monitors Edge computing of the actual data Analysis Analysis & Consideration Equipment Process Level Particle monitor Video camera Knowledge Knowledge must be accumulated Equipment Function Level Laser Particle Monitor Simulation Numerical analysis of defect generation Parts Level Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 25

26 Summary To manage defects, in situ monitors and analysis (edge computing) are key Knowledge must be accumulated from the viewpoint of scientific approach Defect management is needed to be expanded from parts level to fab level Tsuyoshi Moriya / Sep. 9, 2016 / IC Forum 26

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