在上一篇文章中,我介紹了整體公司所使用的製造指標,在這篇文章中我將會介紹常用的監控製造本身的指標,這些指標包含了 在製品,週轉率,每小時產出,以及可生產與非可生產時間.
1.WIP (Wafer in process): This terms are include all the products in your production line. It include the Lot status in "Wait", "Hold", "Running" and didn't include "Bank", "Scrap", "Terminate":Comp".
Wait means the Lot stay and wait equipment process, Hold means the product have some issues need to clarify and it can't move to next step right. a lot of hold product are waiting engineer's resource to re-check or give command for how to handle it. And running, it is the product are processing by equipment. These 3 type status show that, these product can be ship if they finish the whole process.
"Comp" Means that the product are completed all the process, can be ship to customer. It's not include in WIP.
"Bank" is a special status, normally are using in IC foundry, is present the product are stop request by customer. (IC FAB is building to order). Scrap/Terminate are the same thing in our FAB, but scrap is for order products and terminate is for engineer experimental products. These status means it may not ship to our customers. Manufacturing guys are manage WIP's schedule and delivery.
The WIP control normally are control by bottleneck equipment, MFG will control the wafer start (Product input in to production line) Qty. to match the bottleneck equipment capacity. The purpose is wish the WIP are available on line. If we do not control the Qty, the products before your bottleneck will fill your factory building.
1.在製品,這個名詞包含了所有在產線上的產品,他所包含的批貨狀態有"等待", "暫置", "執行中", 但是不包含"移入BANK", "報廢","終止", 以及"完成".
"等待"表示這批貨正在等待設備的加工, "暫置" 代表產品可能有些需要檢查或是因為某些問題無法往下一站移動, 大部分的"暫置"都需要工程師的資源再次的檢查或者給予一些如何處置的指示. "執行中"則代表這批貨正在機台內加工中. 這三種狀態,代表這些貨都是正在產線上跑動,是有機會做完所有的製程出貨的產品.
"完成"代表這產品已經完成所有工廠的加工,可以出到客戶手上了.這也不屬於在製品.
"移入Bank" 是一個特殊用法,通常使用在半導體的工廠中,這狀態代表了客戶要求這些或暫時停下來不要出貨.(半導體的工廠通常是接單生產). 為了不影響產線上的在製品的流動,因此會暫時從在製品的列表上移出."報廢"與"終止" 在工廠內是同一件事情,但是我們將產品的報廢使報廢,而工程品的報廢使用"終止"這三個狀態代表這些貨會在線上停止,報廢繳庫,這些貨不會流到客戶的手上.
製造部的人員通常就是負責管理在製品的排程與交貨.
在製品的管制,通常都是由瓶頸機台的產能來加以考量.目的是希望在製品在線上都是可以流動的. 如果我們不管制再製品的數量,最後在瓶頸機台前的在製品會堆滿整個工廠.
2.Move, One pcs of wafer completed one process step count 1 step move, If wafer completed one stage, called 1 stage move. (Stage such as photo stage include PR coater, exposure, and develop 3 steps). And tool move means tool processed 1 wafer.
We use the gap between actual move and planed move, to forecast the wafer shipping date is behind or lead. Or the daily tool move show the tool status is good or not. The move profile will tell us the tool status and DL human resource locate issues.
Move, 是指一片晶片經過一個站點的處理,計為一個Step Move, 如果是完成一個功能製程，計為一個Stage Move. ( Stage 是比較完整的一小段製程,通常是有特殊的功能,例如黃光製程需要經過 3 step, 光阻塗佈,曝光,以及顯影,這三個步驟完成後我們稱為完成一個Stage), Wafer 經過一台機台的處理稱為 Tool Move.
製造部會去比較我們計畫與實際的Move,並且分析之間的差異,用來預估產品的出貨時間會提前或是落後.或者是每天的Move 比較,用以得知生產線上的機台是否正常運作, Move 分布的型態,可以告訴我們是機台還是人力分配的問題.
3.Turn Rate: The index means that how many stages the wafer can be moved in one day in average. It shows the WIP process speed is good enough, and shows the WIP Qty is reasonable or not. If the WIP too high, the Qty is more than the capacity the production line can be provide. It means we are wast too many cash in line, these WIP can't be moved.
If order are low, MFG will request high turn rate for make up the line operation lost. The reasonable WIP Qty are define by bottleneck tool and cycle time in normal.
For example, 12/25 stage move is 2000, and average WIP is 500, then the turn rate is 2000/500=4.0.
3.週轉率,這個指標所指的是在一天之內,一批貨可以經過多少個Stage, 用來展現 產線的製造速度是否夠理想, 同時也展現出來我們的WIP數量是否合理. 如果WIP太高,產線無法應付這麼多的WIP,則代表我們浪費太多公司的成本在這些在製品上.
當產線的產能利用率低的時候,製造部會要求較高的T/R 來縮減出貨的Cycle time. 通常合理的WIP數量是由瓶頸機台的產能以及產品的cycle time來決定.
4.WPH (Wafer Per Hour), MFG have 2 types WPH in our Daily life, PWPH and AWPH. PWPH Peak Wafer Per Hour, it means the equipment max capability, the throughput without and abnormal in tool. AWPH Actual Wafer Per Hour, the formula = (Daily Tool Move / Tool up time (Hr)). It comes from real equipment performance. MFG will compare PWPH and AWPH to find out the tool efficiency (AWPH/PWPH). If efficiency low than 1 it means 2 possibility, first is tool have some issues abut tool status maintain in wrong status, such as tool "Down" (non-available) but tool status still maintain in "UP". Or the Operator did not run the equipment continually in some type of tool. What if the efficiency large than 1, you should check the PWPH is right or not, or your operator/engineer have a new method to shorter the process time. (normally are not a pass gating review)
4.WPH (每小時產出),製造部會用兩種WPH的指標, 一種是PWPH 理論每小時產出, 他是根據機台正常的狀況下最大產出,通常都是由recipe time 累加而成,工廠內的PWPH會計算到你每天處理不同的貨,使用不同的製程參數所需的時間來計算理論每小時產出. 另一種是AWPH, 實際的每小時產出.計算公式=(當天的機台產出/機台處理貨的時間),這是根據機台的實際表現而來的.製造部會去比較 PWHP 以及 AWPH, 如果這個比值小於一,有兩種可能,一個是機況掛錯,例如機台
已經沒在運作了,但是我們還是掛正在run貨. 或者是作業員在一些可以連續下貨的機台沒有把機台下滿,通常傳送或等待時間就加長. 那如果這個指標大於一呢? 需要請IE單位確認PWHP的時間是否正確,或者有可能是因為你的要求作業員/工程師有了一些新方法可以縮短製程時間(但是通常都是沒有經過檢驗是否可以這樣做的)
5.Available / Non-Available Time, equipment can be use in production or not. Available time include Up, Bkup, Lost, Test. These all are tool can be use in production. Non-Available time are include Down, PM, Wait, Hold, these are tool can't be use in production.
In TSMC it's a critic management on line. Because these indices are reviewed very serious. If Tool down, operation turn the tool status to "WAIT" from lost. (Wait means wait ENG handle), normal the engineer will argue with operation why you change it so fast.
MFG will use these indices to monitor the line operations. We will use some reports to organize these indices to show the status in line. I will introduce these later.
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产品
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