十二吋晶圓自動化搬運系統之高等產品優先服務與搬運時間預估之研究

Abstract

相較於八吋晶圓廠，十二吋晶圓(300mm)製造的產品種類較多樣化。新產品試俥及試產亦較頻繁。同時，製程變更及機台微調的頻率亦增加，需要經常進行製程實驗及產品、設備的監控作業。在生產過程中，此類試驗或工程用晶圓會被賦予較高生產等級，以別於一般晶圓。十二吋晶圓廠必須能彈性地提供高等級產品(hot lot)之作業管理功能，以因應多樣少量的生產型態，然而，目前在十二吋產品主要的搬運系統是懸吊式自動搬運車(OHT)，並無此種功能設計。 本文有兩個主要目標，一是發展出一套有效的OHT派車法則：Preemptive Priority Policy (PPP)，使高等級產品能比一般產品優先處理，第二目標是提出一套有系統的搬運時間預估方式：Modularized Simulation Method (MSM)，來對不同等級的產品進行準確的搬運時間預估。 本文收集台灣某十二吋晶圓廠實務資料並配合模擬來對本文提出的方法進行驗證，結果顯示PPP能有效的將高等級產搬運時間縮短21％且對一般產品的搬運時間沒有顯著影響。而MSM對不同等級的產品推估出的平均搬運時間與模擬結果相當接近，差異在0.1到0.2秒之間。這些實驗結果經由多位台灣十二吋廠的生產製造專家評估驗證後，都給予正面的肯定與評價，這兩種方法對生產線的派工與縮短產品製造時間上有重大的幫助。

Highly automated material handling is one of the most concerns to foundry practitioners because efficient manual operations and coordination have been the core competence in 300mm manufacturing. Especially, one of the critical problems is how to provide an almost no-wait transport for hot lots in an automatic material handling environment. However, there is no effective method for hot lots handling in 300mm Overhead Hoist Transport (OHT) intrabay operation and no effective method to estimate delivery time in 300mm automatic material handling systems (AMHS) operation. There are two objectives of this paper. The first is to develop an effective OHT dispatching method, Preemptive Priority Policy (PPP), to provide the transport services for hot lots against the normal lots transport requirements under 300mm frequently blocking transportation situation. The second objective is to propose an analytic methodology, Modularized Simulation Method (MSM), to estimate the loop-to-loop delivery time for differentiated lots. Simulation experiments based on realistic data from a 300mm wafer foundry are conducted. The results demonstrate that the PPP method can effective expedite the movement of the hot lots for 21% shorter original delivery time. The MSM is also credible in estimating lot delivery times. The time differences between MSM and simulation for both priority lots and regular lots are 0.2 second and 0.1 second, respectively. The results of PPP and MSM have been verified by some 300mm fab managers and are both affirmative.