This article will introduce manufacturing terms, such as Wafer out, CLIP, CVP, FAB yield indices, etc. These indices/terms are daily communication terms in manufacturing. These terms you can find definitions in your text book, I will try to add some actual cases in our FAB.
KPI (關鍵績效指標) 在職涯中是一個很常用/很常見的名詞. 這個指標可以用來衡量工作的表現. 如果你今天是業務員,那麼賣了多少東西就是你的KPI, 如果你是學生,那考試成績就是你的KPI. 本文將會介紹一些製造部常用的名詞,例如 產出,CLIP,CVP, 工廠良率,WIP (在製品), 週轉率,, 製造循環時間等. 這些名詞都是製造部日常溝通的用語.這些名詞你可以找到教科書上的定義,但是我試著介紹在工廠內是如何使用這些名詞或KPI的方式在本文中介紹.
The most important KPI in manufacturing.
1.Wafer Out(產出): In IC foundry or LED industrial we count the output by wafer. The product size is not a fixed number in FAB, can't reflect the real loading in line. All the IC/LED tool are processing wafers, so using wafers to count the output is a better method than dices.
The definition for Wafer out is the wafer count for pass the Out going QC's examining and shipping to goods inventory's. the unit is pcs, in manufacturing we publish the wafer out indices by daily/weekly and monthly. It means that how any good wafers can be ship out in the period.
1.晶片產出: 在 IC 代工或者LED 的產業,我們通常使用晶圓數來計算,因為最終產品的尺寸是不固定的,而且機台也都使用於處理晶圓. 所以我們使用晶原來代表工廠內的產能負載.
晶片產出的定義:通過 OQC 檢驗可以入到成品倉的晶圓數量. 計算的單位是片. 在製造部我們每天/每周/每月都會公布產出的數字. 對於公司來說會以成品倉所公布實際收到的晶圓數作為實際產出.通常製造部與成品倉兩邊的數字是一致的.
這個指標所代表的意義是,在這段期間內我們產出了多少可以出貨的晶片.
2.Cycle time (C/T): The time from wafer start to build until pass the OQC examining. the unit is day (for IC/LED). The formula is Cycle time = pass OQC's time - wafer start to build time. The index shows that how fast you can complete the whole processing.
We also watching C/T per layer this index, it shows the time need for complete one photo layer process. In semi-conductor industrial photo layer are the most important process, the photo layers number present the how complex the product are. the formula = Cycle time / photo layers number. for example, C/T is 8 days, photo layer is 10, the cycle time per layer =8/10=>0.8 day.
Using the C/T per layer for compare different product's C/T performance. For example Product A C/T 10 days, Product B C/T 8 days, it seems Product B is better than A, but we consider the photo layers, Product A with 10 layers and Product B with 4 layers. Product A C/T per layer = 1 day, Product B C/T per layer =2 days.
2.生產週期:從下線到完成出貨品檢的時間,單位是天. 計算公式是 完成出貨檢驗的時間減掉下線的時間. 這個指標代表了你多快可以完成全部的製程.
我們也同時會注意每層黃光製程週期的時間,這個指標的定義是產品在兩層黃光間所花費的時間. 計算方式是 生產週期/產品的光罩道數.
因為半導體製程都是由一層一層堆積而成,每一層都需要黃光製程.所以黃光的層數也可代表這個產品的複雜度.;
3. FAB Yield: It's a quality index, the definition is the ratio between wafer out (include wafer in outgoing SPEC and ship-able Qty) and wafer start Qty in the period. the formula = ( Wafer ship Qty) / (Wafer Ship Qty+Scrap Qty) in period. the unit is %. (Why the numerator is not wafer start Qty? Ans because of the product fabrication time maybe larger than the compute time period, in a mass production FAB it will be very close) MFG provide this index daily/weekly and monthly.
For example, MFG wafer shipp Qty. = 99pcs, scrap 1 pcs, the FAB Yield = 99/(99+1) = 99%.
3.工廠良率:這是屬於品質類的指標,他的定義是統計期間內工廠產出可出貨/符合出貨規格的良品數量與投入生產的產品數的比例. （包含客戶特採）,公式是 工廠良率＝（晶片產出數量）/（晶片產出數量+晶片報廢量）單位是％. (分子為何不是使用晶片投產量？原因是生產的週期可能大於統計期間,所以使用產出量當作分子.在一個大量投產的工廠內,這個數值應該是相當接近實際投產數值）計算期間是每日/每週/每月.
舉例來說造部產出的片數是99片,統計期間報廢了一片,所以 99/（99+1）＝99％,工廠良率就是99％.
4. WAT Yield: Wafer Acceptance Test (WAT) Yield, It means the wafer pass WAT test's ratio in the period. WAT test is a special test before deliver to OQC in FAB, it's not full function test (it's CP test/ CP yield). It test designed circuit by prober on the wafer. Passing the test means FAB's machining are correct. The formula = (Pass WAT wafer count)/(WAT Test wafer count), the uint is %.
4.WAT 良率: 電性允收測試, 這個指標所指稱的是在統計期間,通過WAT測試的比例. WAT是在交給OQC前的特殊測試,他並非全功能的測試,他是在切割道上所設計的測試線路,如果通過這個測試則代表工廠內加工的程序是正確的.
計算公式＝（WAT測試合格的片數/測試晶片的總數）
5. F-CLIP :Fab Confirmed Line Items Performance, it shows the capability of FAB follow PC (Product Control Dept) MPS (Main Production Schedule). PC request MFG to delivery the products with different shipping date and Qty for different orders/batch. The ratio for each items meet or not is our F-CLIP.
F-CLIP = (on time or early deliver items) / (total items) unit is %
For example : PC request MFG delivery schedule as following:
9/7 100, 9/14 100, 9/21 100, 9/28 100 => Total delivery request Qty is 400.
And MFG deliver status
9/7 40, 9/14 100, 9/21 100, 9/28 80 => Total actual delivery Qty. is 320
Only 9/14 and 9/21 are meet the item request 9/7 and 9/28 are fail => F-CLIP = 2/4 = 50%
5. 工廠準時達交率：工廠依據生產管理部所排定的交貨時程準時或提前的能力指標.生產管理部會要求製造部依據不同的訂單/交貨批次排定不同的交貨時間及數量. 準時達成交貨數量的次數與要求交貨的次數的比例就是工廠準時達交率.
工廠準時達交率＝ （提早或準時達交次數/預定交貨的次數）
舉例來說,PC 排程如下
9/7 100, 9/14 100, 9/21 100, 9/28 100 => 總排定交貨量是 400.
製造部實際交貨的數量如下：
9/7 40, 9/14 100, 9/21 100, 9/28 80 => 總實際交貨量 320
只有 9/14 及 9/21 兩天是達交的,而 9/7 及 9/28 是未達交的
工廠時達交率＝2/4＝ 50%
6.F-CVP: FAB confirmed volume performance, FAB capability of follow PC's monthly delivery Qty.
F-CVP= Delivered Qty./Planed Delivery Qty unit is %.
as the CLIP's sample the F-CVP = 320/400 = 80%
6.工廠產量達成率,工廠達成生產管理部所訂定的每月交貨量能力.
工廠產量達成率=當月交貨量/當月預計交貨量
以上例而言, 工廠產量達成率＝ 320/400 ＝80％
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