©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 Analysis of Circular Cluster Tools: Transient Behavior and Semiconductor Equipment Models Younghun Ahn and James R. Morrison KAIST, Department of Industrial and Systems Engineering IEEE CASE 2010 Toronto, Canada August 22, 2010

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 2 Contents Motivation System description: Cluster tools Methods – Transition analysis – Waiting times in the transitions – Cycle time analysis & simulation Concluding remarks

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 3 Motivation Semiconductor wafer fabrication is arguably the most complex of manufacturing processes with facility costs rising toward US $5 billion Transient behavior in semiconductor manufacturing will be much more common – Until now, there has been substantial effort to model and control tools in steady state – Transients are brought about by setups, product changeovers and small lot sizes (few wafers per lot) – In the current & future, transient behavior is more common/frequent Goal: To develop rigorous models of wafer cycle time in cluster tools that include wafer transport robot and address transient behavior

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 4 Motivation Existing research – Single-wafer Cluster Tool Performance: An Analysis of Throughput* It doesn’t consider robot put / get time It assumes that all chambers have same process time We will call the PMGC approximation – Throughput Analysis of Linear Cluster Tools** It doesn’t consider robot move, put / get time ( E is the alternative) It assumes that all chambers have same process time We will call the PM approximation Our research * T. Perkinson, P. McLarty, R. Gyurcsik, and R. Cavin, “Single-Wafer Cluster Tool Performance: An Analysis of Throughput,” IEEE Transactions Semiconductor Manufacturing, vol. 7, no. 3, pp. 369–373, ** P. van der Meulen, “Linear Semiconductor Manufacturing Logistics and the Impact on Cycle Time,” in Proc. 18th Ann. IEEE/SEMI Adv Semiconduct. Manuf. Conf., Stresa, Italy, Achievement We consider robot move time, get / put time and different process time We make a general equation and cyclic approximation

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 5 System Description Backward policy is considered Wafer lots consist of up to 25 wafers Each wafer must receive service from all process chambers in sequence Robot move time is constant C1C1 C2C2 C3C3 C4C4 loadlock aligner WTR VEC Circular cluster tool

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 6 R X,Y,Z, X: Robot action, Y: Index of wafer, Z: Location – X ∈ {G, P, M, W}, Y ∈ {0, 1, …, W}, Z ∈ {I, O, C 1, C 2, …, C N } – W Ci (w j ): Duration of time the robot waits after it reaches chamber i until wafer j is completed and ready for removing – δ: Robot move time – ε: Robot get / put time – P i : Process time of chamber I A j, j ∈ {0, 1, 2, …, N} – Robot action of removing a wafer from chamber and placing it into chamber j+1 – A B =(A N,A N-1, …, A 1, A 0 } Transient control: use “backward sequence“ and systematically skip action that are not possible System Description M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput A1A1 M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput ABAB

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 7 Transition Analysis R G,1,I → R M,1,C1 → R P,1,C1 → R W,1,C1 → R G,1,C1 → R M,1,C2 → R P,1,C2 → R M,0,C2 → R G,2,I →… → R P,W,O M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput M4M4 M3M3 M1M1 M2M2 inputoutput Example of robot behavior (initial part of robot sequence) ※ T X,Y,Z is the instant time at which event R X,Y,Z completes

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 8 Transition Analysis Lemma 1: Duration of the initial transition & cyclic period Proposition 1: General equation for the cycle time NOTE: we develop a recursive procedure to calculate W Ci (w j ) in paper NOTE: we also find out the duration of the final transition in paper (Lemma 2)

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 9 Cycle Time Analysis & Simulation Idea for approximation – 1-unit cycle time for N chambers (backward sequence)* Our approximation Approximation 1: Cyclic approximation for cycle time * * W. Dawande, H. Neil Geismar, P. Sethi, C. Sriskandarajam, “Throughput Optimization in Robotic Cells”, Springer, * P2P2 3δ+4ε P 2 +3δ+4ε t

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 10 Cycle Time Analysis & Simulation Approximation 2: PMGC Approximation for Cycle Time Approximation 3: PM Approximation for Cycle Time Modified version of existing approximation

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 11 Cycle Time Analysis & Simulation Application: Semiconductor wafer cluster tools – Measurement: The average time between lot departures (TBLD) – TS (Train size): The number of lots that are run consecutively – Simulation: 400 lots, 20 replications – Example 1: N=4, P 1 =80, P 2 =70, P 3 =110, P 4 =90 δ=1, ε=1

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 12 Cycle Time Analysis & Simulation Application: Semiconductor wafer cluster tools – Example 1: N=4, P 1 =80, P 2 =70, P 3 =110, P 4 =90 δ=1, ε=1 μs CPU time(μs) in Example 1

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 13 Cycle Time Analysis & Simulation Application: Semiconductor wafer cluster tools – Example 2: N=4, P 1 =6, P 2 =5, P 3 =4, P 4 =5 δ=1, ε=1

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 14 Concluding Remarks Contribution – Exact equation: Transient analysis is possible – Cyclic approximation is less errors than existing approximations – Our models are good candidates for use in semiconductor manufacturing modeling and simulation Future direction – Study other robot sequence for transient state – Consider parallel circular tool

©2010 – IEEE CASE 2010 – Toronto – August 22, 2010 – 15 Question & Answer