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Introduction

Integrated Circuits Cycle Time at Test Operation Estimation for Production Planning using Computer Simulation By Jitrayut Junnapart. Introduction. Introduction(1): Assembly Process. General Process of IC manufacturing:. Introduction(2): Electrical Test Process.

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Introduction

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  1. Integrated Circuits Cycle Time at Test Operation Estimationfor Production Planningusing Computer SimulationByJitrayut Junnapart Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  2. Introduction Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  3. Introduction(1): Assembly Process • General Process of IC manufacturing: Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  4. Introduction(2): Electrical Test Process • All products must be 100% tested before deliver to customers • Electrical Test process is shown below: Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  5. Introduction(3): Electrical Test Time • Test Time depends on: • Test Rate at main flow (in Units Per Hour) • First Pass Yield (0 to 1 for 0% to 100%) • Test Rate at rescreen flow (in UPH) To P.15 Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  6. Introduction(4): An Example • Suppose one production lot of: • 3,000 units • Main Flow Test Rate = 1,000 UPH (Units Per Hour) • Rescreen Flow Test Rate = 300 UPH • First Pass Yield = 90% • Calculate Cycle Time: Main Flow Test Time= 3,000 / 1,000 = 3 hours Rescreen Flow Test Time= [ 3,000 * (1 - 0.9) ] / 300 = 1 hour Total Test Time= 3 hours +1 hour = 4 hours Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  7. Introduction(5): Why interesting? • Electrical test time is very important because it dominates overall IC manufacturing cycle time • There are methods to calculate cycle time: • Use average values (of UPHs, FPY) • Apply simulation method • Others Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  8. Literature Review Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  9. Literature Review(1) • This project applies Monte Carlo Simulation based on historical data of: • Main flow test rate • Rescreen flow test rate • First pass yield to simulate for total cycle time of one production lot Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  10. Literature Review(2) • Monte Carlo simulation uses random number to “pick” one value of data as a representative for further calculation Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  11. Literature Review(3): Example • Suppose we want to simulate main flow test time • And partial of historical data of main flow test time (in UPH) looks like: Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  12. Literature Review(4): Step 1 • Rearrange the numbers into frequency and probability table: Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  13. Literature Review(5): Step 2 • Construct cumulative probability table from probability table: Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  14. Literature Review(6): Step 3 • Set up probability intervals for ranges of UPH: Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  15. Literature Review(7): Step 4 • Generate a random number and map onto the appropriate interval to find a simulated value of main flow UPH Random No. generated is 0.5934 Simulated UPH = 160 Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  16. Literature Review(8): Step 5 • Repeat step 1-4 but for: • First Pass Yield and • Rescreen Flow UPH • Use equation in slide 5 to calculate Simulated Total Test Time Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  17. Literature Review(9) • BUT real test rate (UPH) data is continuous number (appendix C,p79) • We need to group them first into ranges • Then count number of data that are in each range • And find the center value of the group as a representative number of the group Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  18. Literature Review(10) • Number of group can be chosen • Groups shall cover every data See appendix D, p.86 for detail Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  19. Project Development Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  20. Project Development (1) • Problem Definition: • Electrical test time is the main dominator of overall production cycle time in back-end IC manufacturing • Cycle time affects shipping commitment to customers • Using average test time is not effective because the numbers vary over wide range Production control people wants a tool to forecast electrical test time of the IC Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  21. Project Development (2) • Objectives: • To develop computer software that processes historical test rate data (in Units Per Hour - UPH) at main flow and rescreen flow, and first pass yield (retest rate-related) from production and simulate for probability to finish testing a production lot with various allocated time. • The computer software must be separated into main program and auxiliary data files. The main program will work with various environments without modification. • The developed simulation program code must work on both Personal Computer (PC) and larger computer running on UNIX operating system. Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  22. Project Development (3) • Scope and limitations of the project: • It is considered that main flow test rate, rescreen flow test rate, and first pass yield being input of this project are available beforehand. They are stored in separated text files which, in fact, easy to develop the system further. • This project gives calculation output as a text file for easy to use in the future. Example of this is putting into Hypertext Markup Language (HTML) and post on facility’s Intranet. • The software in this project will calculate for success probability to finish electrical test process based on a certain size of production lot. User can later use linear relationship to calculate for other size. Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  23. Project Development (4) • Project Time Line: • The project consists of 9 major tasks • Total time taken is 7.5 months Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  24. Project Development (5) • Feasibility Study: • Technical » Feasible • The champion has knowledge of simulation and programming language • Economic » Feasible • The project does not require special expenses • Operational » Feasible • The project does not interfere the normal work practice of concerning people • Legal » Feasible • Software used in development is legal and all data is legally used Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  25. Project Implementation Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  26. Project Implementation (1) • Concerns • Output must be easy for user to understand • Test time depends on lot size, and it is not feasible to provide all lot sizes output • User should have control over some essential simulation parameters • Change in source code is undesirable 1,2 3 4 Need modifications Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  27. Project Implementation (2) • To solve concerns #1 and #2 To concerns • An allocated time is set • The simulated test time for a certain lot size iscalculated and compared to a allocated time. If test time is shorter than allocated time, the result is possible. This 'success number' is counted. • Repeat step 2 for many times and calculate success chance from success times and total simulation times and report this chance to user. • Increase theallocated time by delta defined • Repeat step 2 to 4 for certain rounds defined Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  28. Project Implementation (3) • To solve concerns #3 To concerns Store simulation parameters in file para.txt • Number of types of IC to perform simulation • Number of divisionsto group historical data • Lot size that simulation is based on • Number of repetitive simulation for one allowable time • Start point of allowable time • Increment of allowable time • Steps of increment of allowable time Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  29. Project Implementation (4) • To solve concerns #4 To concerns All input data are stored in separated files: • Historical files of Mainflow UPH (.mnf) • Historical data of Rescreenflow UPH (.rsf) • Historical data of Firstpassyield (.rrf) • List of IC types file (progname.lst) Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  30. Project Implementation (5): Files • Main flow UPH file icname.mnf • Rescreen flow UPH file icname.rsf • First pass yield file icname.rrf • List of icname file – progname.txt • Parameters file – para.txt Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  31. Project Implementation (6) Open file “progname.lst” and para.txt that stores test program names to simulate and read all the names and parameters Processed for every test program? End Yes No 1.Open file that stores UPH Main flow, and read all main flow UPH for next program 2. Count number of data 3. Divide into divisions 4. Calculate for accumulated probability 5. Repeat step 1-4 but for rescreen rate and UPH of rescreen flow 1.Simulate total time used to test the production lot 2.Count for number of success that the time used is less than allocated time 3. Repeat 1 and 2 and calculate success probability 4.Record result in output file 5.Increase allocated time Simulation Method Allocated time > limit? No Yes Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  32. Project Implementation (7) • Programming • Coding is done in ANSI C language • Length of the program ~900 lines • Special statements and commands are avoided for the program can run both on PC and UNIX based computer system Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  33. Simulation Result Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  34. Simulation Result (1) 1) Screen output • PC based result: Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  35. Simulation Result (2) 2) File output (result.txt) • PC based result: Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  36. Simulation Result (3) Compiled program • Unix Based result Control parameters input Printed out for monitoring Screen output Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  37. Simulation Result (4) • Unix Based result Output file Generated Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  38. Simulation Result (5) • Unix Based result bkkeis{pemg}34: vi result.txt Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  39. Project Evaluation Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  40. Project Evaluation (1) • Verification of Objectives: • Output is easy for non-engineering people to understand  Yes • Control parameters used in simulation can be input to program through external file  Yes • Various simulations can be performed without any changes to main program  Yes • The source program can be compiled to work on both PC and UNIX based computer  Yes Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  41. Project Evaluation (2) • Verification of Result: • The simulated result is verified back to historical data • The result is 3-5% deviation • This is very good for simulation (probabilistic work) Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  42. Conclusions • Simulation technique can generate result that gives adequate accuracy (3-5% error in this work). The result can be transform in the way that it is easy to understand by end user. • The planner (user) can assign allowable time to test production lot based on his/her confidence level that the lot will finish in time • In this particular work, essential parameters in simulation can be changed easily in control files without modification to the main program Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

  43. Random Number Generation • Confirm the even distribution by JMP 1,000 numbers 10,000 numbers Cycle Time at IC Electrical Test Operation Simulation by Jitrayut Junnapart

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