Managing Multi-chamber Tool Productivity Bruce Auches, Gulsher Grewal, Peter Silverman Intel Corporation Santa Clara, Ca. This paper appears in: Advanced Semiconductor Manufacturing Conference and Workshop, 1995. ASMC 95 Proceedings. IEEE/SEMI 1995 Publication Date: 13-15 Nov. 1995 Page(s): 240 – 247 OR Seminar Presentation Teacher: Pros. 陳茂生, Pros. 阮約翰 Student: 937807 張幼蘭 2005/4/21
Introduction • Because the operational economic benefits, Multi-chamber tools became popular nearly in a decade. • Used in Thin- film, Etching, Testing fields.
PM Various run scenarios PM Time Run/PM cycle Measurements of Productivity • Run Rate: output wafer per hour (wph) • Run/PM Cycle Motivation: help tool user to make decision of repairing or ignoring failure chamber that maximize productivity.
Delimit Problem Boundary (1/3) • Focus on parallel configuration.
Delimit Problem Boundary (2/3) • Parallel processing mode can run by other available chambers.
Delimit Problem Boundary (3/3) • Scheduled PM is triggered by fixed processing wafer quantity. • Quantity base PM: metal deposition, poly etching… • Time base PM: photo exposure
PM PM Time Chamber Failure Run/PM cycle Responses of Unexpected Chamber Failure Incident (1/3) • Full Cluster Operation (FCO): take down tool completely to repair failure chamber. • Necessary if: • Central component fail • Cannot repair while the rest tool run Take down to repair Full Run Full Run
PM PM Time Chamber Failure Run/PM cycle Responses of Unexpected Chamber Failure Incident (2/3) • Partial Cluster Operation (PCO): defer to repair failure chamber and keep good chambers running until next PM. • Necessary if: • Cannot repair while the rest tool run Defer repair and keep Partial Run Full Run
PM PM Time Chamber Failure Run/PM cycle Responses of Unexpected Chamber Failure Incident (3/3) • Run/Repair Operation (RRO): repair failure chamber while the rest tool runs. • May or may not be feasible depending on safety issue and failure position. Repair with Partial Run Full Run Full Run
Fixed Variables (1/2) • Tool Run Rate • Full Cluster Run Rate (FCRR) • Partial Cluster Run Rate (PCRR) • As FCRR decreases, FCO is favored. • Mean Wafers between PM (MWBPM) • Visiting wafer quantity between PM for each chamber. • As MWBPM increases, FCO is favored.
Fixed Variables (2/2) • Major PM Duration (tPM) • As long as one chamber finished MWBPM wafers, major PM is triggered. • As tPM decreases, FCO is favored. • Number of Process Modules (n) • Count “Parallel Path” • As n decreases, FCO is favored.
Failure-dependent Variables • Time to Repair (MTTR) • Duration of repairing failure chambers • As MTTR decreases, FCO is favored. • Wafer Count (%F * MWBPM) • Processed wafers quantity before chamber failed. • As %F increases, FCO is favored.
Output Evaluation Formulas(1/4) • W = number of wafers processed in a complete “run/PM” cycle • C = total time in a “run/PM” cycle • Output = W/C • Higher output is favored
Output Evaluation Formulas(2/4) • FCO • WFC = MWBPM * n • CFC = tBFFC + MTTR + tAFFC + tPM • tBFFC: Time before failure tBFFC = (%F * MWBPM * n) / FCRR • tAFFC: Time after failure tAFFC = ( ( 1 - %F ) * MWBPM * n) / FCRR
Output Evaluation Formulas(3/4) • PCO • WPC = WBFPC + WAFPC • WBFPC = MWBPM * n * %F • WAFPC = MWBPM * ( n–1 ) * ( 1- %F ), assume one chamber/path fail for example. • CFC = tBFFC + tAFFC + tPM • tBFFC = (%F * MWBPM * n) / FCRR • tAFFC = ( ( 1 - %F ) * MWBPM * (n-1) ) / PCRR
Output Evaluation Formulas(4/4) • RRO • WRR = WBFRR + WDFRR + WAFRR • WBFRR = MWBPM * n * %F • WDFRR = MTTR * PCRR If MTTR is long enough that other good chambers/paths reach PM, then WDFRR = WAFPC. • WAFRR = [ MWBPM - WBFRR/n - WDFRR/(n-1) ] * n • CFC = tBFRR + MTTR + tAFRR + tPM • tBFRR = (%F * MWBPM * n) / FCRR • tAFRR = WAFRR / FCRR
Example (1/3) • Values for variables: • n = 2 • FCRR = 20 wph (wafers per hour) • PCRR = 10 wph • tPM = 10 hr (hours) • MWBPM = 500 wafers per chamber/path • %F = 20% • MTTR = 10 hr
Example (2/3) • Output calculation: • FCO: 1000 wafers / 70 hr = 14.3 wph • PCO: 600 wafers / 60 hr = 10.0 wph • RRO: 900 wafers / 60 hr = 15.0 wph • RRO is the best decision if it is feasible; otherwise, FCO is suggested to choose. • Deferring repair would cause 30% of FCO output loss and 50% of RRO output loss.
Sensitivity Analysis (1/4) • At most time, the RRO is the best strategy; PCO become the best when the MTTF is longer than the time of processing (1-%F) wafers. • In previous example, the “break-even point” of RRO and PCO is at %F = 80%; FCO and PCO is at 72%.
Sensitivity Analysis (3/4) • Longer MTTR or later failure timing (bigger %F) lead to choose PCO; or else, lead to choose FCO. • Using the data in previous example, it can be plot a “break-even curve” of FCO and PCO corresponding to %F and MTTF. Above the curve PCO should be employed; below the curve FCO should be employed.
Conclusion • Tools should be designed to enable the RRO where successfully maximize output in most cases. • PCO availability should be minimized in most cases. The root causes of the premature failures should be aggressively sought out and fixed. • If RRO is not feasible, tool user should calculate the “break-even curve” to help make decision more quickly.
Further Study • Multiple multi-chamber tool repair decision process • Other site unbalance problems