D4 - Process Mapping

Six Sigma
Process Mapping
Process Mapping
Process mapping is an essential tool in helping us understand the activities and sequence of steps involved in any process. It also helps to identify areas where data collection should take place. It is commonly used at the early stages of project definition or project development to visualize the activities involved in a process. By completing the process map prior to performing process baselining and calculating the Sigma value, we can focus on processes that we fully understand. By comparing the “as is” against the “ideal” process diagram we can identify opportunities for improvement such as simplification of a complex process or elimination of non-value added operations. The standard set of symbols presented herein are a starting point and, as our experience grows, we can add some other symbols to draw diagrams of various levels of detail to better understand and visualize the process. The CT tree is linked to this tool making it useful for all levels of an organization. Six Sigma Champions can utilize this tool to visualize the process steps that may impact a Critical To Satisfaction (CTS) characteristic, while a Six Sigma Black Belt or team member would utilize this tool to visualize the impact on Critical to Quality (CTQ) characteristics. At the system level where a product is a function of processes, the process map defines a series of processes, whereas at the sub-system level, where processes are a function of operations, a process map represents operations that are linked. This section includes the general Process Flow Diagram, two of its variations and the “Process Flow Format,” which provides a standard form to record and analyze the activities of a process. The “Macro Flow Diagram” is a general view of the process. Only general descriptions of the steps are included with no decision points. The “Deployment Flow Diagram” identifies the individuals or departments responsible for the activities and the sequence in which these activities take place in the process.
Key Questions

? ? ? ? ? ?
What is a "process map" and how does it connect to CT and defect opportunities? What role does a process map play when making improvements? What are the primary benefits associated with the use of process maps? What are the key elements of a process map? How much detail should be added to a process map? How should a process map be put together?
Key Questions A process map has many uses in Six Sigma. For example, it is related to the CT and Opportunity for Defect concepts in that after identifying the CTQ, CTD, and CTC characteristics, it depicts the sequence of steps or activities that a product or service follows and the complexity level of the process that produces the deliverable. It can also be used to identify those areas where defects are likely to occur and data collection points. Much like the CT tree, a process map may have various levels of detail. At the system level, the process map depicts linked processes (a product is a function of processes), whereas the subsystem level represents operations that are linked (a process is a function of operations). There are various types of process maps. The Macro Flow Diagram is a general version that shows only major activities without any decision points. The deployment version identifies the sequence and persons responsible for completing each activity. The tabular version (process mapping format) allows us to compare "observed" against "target" values of a process map. Since they are based on standard symbols, process maps provide a simple picture of the steps needed in completing a deliverable. Moreover, when the “as is” version is compared against the “ideal” version, simple but significant improvements may be identified. All process maps have some key elements, regardless of the nature of the product. Start and end points, activities, decision points and connectors are common to all process maps. To ensure that a map is accurate and complete, it is recommended that the input of all team members be considered and validated.

Process Flow Diagram
VA
Begins Return for rework Load skins in racks Inspect Install in jig and drill
A
VA
VA
Manual rivet, identify and mark
A
Apply spray dot Rework dots
Verify prior trim
Trim, remove lug, deburr, clean & apply sealing
B
VA
VA
Apply liquid shim Final drill, contersink
B
Drill identification holes
Automatic riveting
C
VA
1_02_04_002
Process Mapping
Process Flow Diagram In order to improve the customer’s CTS (Critical To Satisfaction) characteristic “aircraft appearance,” a Champion and a Master Black Belt were studying the possibility of launching a Six Sigma project in the assembly area of the CRJ aircraft model. Following customer feedback, they decided to further refine this CTS characteristic as “skin appearance,” and they decided to concentrate on the mid-fuse section. The number of scratches per skin was defined as the CTQ (Critical To Quality) characteristic and a Six Sigma project was launched. The Six Sigma Black Belt knew that, in order to define the current defect-per-unit level, she needed to collect data. So she gathered the Six Sigma team to draw a Process Flow Diagram. During a brainstorming session, the team identified the standard as a skin having zero scratches. They also agreed that the activities to study would be bound by those taking place in a particular assembly department. After having identified all the steps that take place in the department, they used the standard symbols to draw the Process Flow Diagram. The team decided to organize data collection at the following steps: a) load skins in racks; b) apply spray dots; c) drill and apply liquid shim; and d) scratch repair. Collecting data prior to the inspection points allowed the team to assess the “hidden factory.” In deciding which steps add value, the team considered a) Does the customer recognize it as important and would he/she pay
DEFINE
4
C
Fastener/ bracket installation
Clean, ident. and scratch repair
Inspect
Ship to next step
Ends

for it if asked? b) Does the step change the product/service physically? and c) If done right first time, would this step be necessary? The following were identified as non-value operations: a) inspection; b) application of liquid shims; and c) rework dots. Thus, possible improvements were identified at early stages of the project.
Process Mapping Format
Deliverable Process Champion Department Organization Project Facility Generic Widget Product Total Manaufacturing Joe Toofast ABC XYZ NA Alwayslost , Idaho
Step 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Step Description Receive steel Perform inspection Complete documentation Trasport to cut-off Execute cut-off operation Perform inspection Rework as required Complete documentation Trasport to milling Execute milling operation Perform inspection Rework as required Complete documentation Transport to assembly Execute assembly operation Perform inspection Rework as required Complete documentation Transport to shipping Total = Efficency =
Work Verify X
Fix
Move
Delay
Store X
Unit Description Steel bar stock
Dist
Time 37.2 5.5 1.4
OP
X X X X X X X X X X X X X X X X X 3 16% 4 3 4 4 1 478 1,362 Finished Widget 265 Finished part 382 Steel cube stock 237
5.3 7.7 1.5 4.6 0.5 11.4 5.6 1.2 1.5 0.5 8.7 1.7 0.3 0.8 2.5 12.4 110.3
Process Mapping
Process Mapping Format Meanwhile, another Six Sigma Black Belt used the Process Flow Format to prepare a detailed analysis that included the distance traveled and the time required to complete the steps involved in his project. Using some of the concepts presented during the Six Sigma training, the Black Belt agreed with production and management personnel to observe, record, and analyze the steps involved in the milling and assembly of the subject product. After having completed the form as shown above, the analysis shed light on the fact that the process had an efficiency level of only 16%. That is, only three steps out of a total 19 were identified as “work,” or "value-added operations." The next step in the Black Belt’s project was to obtain the target levels from the organization in terms of distance and time for the process. With this input, possible improvements to reduce time or distance can be identified and implemented.
DEFINE
5

Deployment Flow Diagram
Business Unit
Define needs Prepare paperwork (CAAR & installation request) Review & approve CAAR Receive & use
Review & approve standard CAAR > $50,000
I.T.
Configure & install
Finances
Review & approve CAAR
Issue payment
Top Mgt/ Corporate
Review & approve CAAR
Procurement
Acquire equipment
Supplier
Supplier
21 days
6 days
15 days
5 days
17 days 7 days
71 days
Process Mapping
6
Deployment Flow Diagram A Six Sigma Champion responsible for the procurement of computer equipment was wondering if a Six Sigma project could be launched in his area. Working with a Master Black Belt, they singled out cycle time of the acquisition process as the CTS characteristic. Their first task was to identify the length of time that it currently takes to procure computer equipment for their various clients. Once they agreed on the general steps of the process, the Master Black Belt assisted the Champion with the analysis of preliminary data, and they determined that the acquisition process currently takes 71 days from definition of needs to receipt of the equipment by the customer. Further analysis revealed that definition of needs, paperwork preparation, and approval by the business unit represented 30% of the cycle time, while approval by the Finance department represented 20%. The Procurement/Supplier process represented an additional 30% and IT spent the remaining 20% approving the standard and installing the equipment. Having identified these elements, the Champion and the Master Black Belt knew that one or various Six Sigma projects could be launched in relation to this business process.
DEFINE

Step Reduction Through Process Mapping
Issue raw material Inspect not ok ok Rough saw material Transport to deburr Deburr Transp. to stretch press
Stretch form complete
Hold in freezer
Transport to freezer
Heat treat to AQ cond.
Transport to heat treat
Stretch form
Hydroform
Insp on CF not ok
ok
Transport to saw
Saw net
Transport to deburr
Deburr
Machine
Transp to m/c shop
ok
hardness check not ok
Transport to insp.
Age
Transport to age
not ok Transp to deburr Deburr Transport to insp. Insp ok Transp to finish Chemical clean
Transp to store
ok
Insp
Part marking not ok
1_02_04_005
Back to area resp.
Process Mapping
Step Reduction Through Process Mapping A Six Sigma Black Belt is assigned to a project with the objective of improving the quality of parts used in the assembly area. To narrow the scope of the project, the team decided to focus on reducing the amount of shimming used to close gaps and mismatches between ribs and spars. To better understand the existing process, one of the steps the Black Belt did was to draw the “as is” process map. Upon further analysis and discussion, the team proposed a series of changes to reduce the number of operations required to fabricate the components. Some of the modifications include: ? Changing the raw material to T6 condition, thus eliminating operations for heat treating and delays in freezer storage; ? Producing the parts in the machine shop instead of stretch forming, thus combining almost all fabrication steps, eliminating the need for multiple deburr operations and combining inspection steps. By utilizing this relatively easy but powerful tool, the team was able to obtain some quick improvements, reduce the complexity of the process and increase the capability of the CTQ. This tool can be used by all levels in the organizations (i.e., Champions, Master Black Belts, Black Belts, etc.) and is applicable to all areas of the business (i.e., manufacturing, transactions, engineering, etc.).
DEFINE
7
Primer application
Chemical film

Lessons Learned
? ? ? ? ? ? Process mapping is a tool that applies to all types of projects (manufacturing, transactions, engineering, etc.). The expertise of all members can add value to the process map. Working with a team we ensure the “as is” process is represented, and the opportunities for improvement are identified. Various levels of the organization can benefit from the use of process maps. Champions can better identify and define opportunities for Six Sigma projects, and Black Belts can understand and improve actual processes. By linking process maps to the CT tree and to performance specifications, we can identify the areas where defects are likely to occur and we can establish data collection points to better record and assess current defect levels and improvements. At the system level of the CT tree, a process map represents a service of linked processes. At the subsystem level, a process map represents a series of linked operations.

研究生《高等半导体器件物理》试题

2014级研究生《高等半导体器件物理》试题 1.简单说明抛物线性能能带和非抛物线性能带的能带结构以及各自 的特点、应用。 2.试描述载流子的速度过冲过程和弹道输运过程，以及它们在实际 半导体器件中的应用。 3.什么是半导体超晶格？半导体器件中主要的量子结构有哪些？ 半导体超晶格:两种或者两种以上不同组分或者不同导电类型超薄层材料,交替堆叠形成多个周期结构,如果每层的厚度足够薄,以致其厚度小于电子在该材料中的德布罗意波的波长, 这种周期变化的超薄多层结构就叫做超晶格. 主要的量子结构:超晶格中, 周期交替变化的超薄层的厚度很薄,相临势阱中的电子波函数能够互相交叠, 势阱中的电子能态虽然是分立的, 但已被展宽. 如果限制势阱的势垒进度足够厚, 大于德布罗意波的波长, 那么不同势阱中的波函数不再交叠, 势阱中电子的能量状态变为分立的能级. 这种结构称之为量子阱( QW).在上述结构中,电子只在x 方向上有势垒的限制, 即一维限制,而在y , z 两个方向上是二维自由的. 如果进一步增加限制的维度,则构成量子线和量子点. 对于量子线而言, 电子在x , y 两个方向上都受到势垒限制; 对于量子点来说, 在x , y , z 三个方向上都有势垒限制. 我们通常将这些量子结构称为低维结构, 即量子阱、量子线和量子点分别为二维、一维和零维量子结构. 4.PHEMT的基本结构、工作原理以及电学特点。 5.隧道谐振二极管的主要工作特点，RITD的改进优势有哪些？ 6.突变发射结、缓变基区HBT的工作原理、特点及其应用。 7.举例讨论半导体异质结光电器件的性能。

参考文献： 1.沃纳，半导体器件电子学，电子工业出版社，2005 2.施敏，现代半导体器件物理，科学出版社，2002 3.王良臣等，半导体量子器件物理讲座（第一讲~第七讲），物理（期刊），2001~2002

半导体器件物理

半导体器件物理 Physics of Semiconductor Devices 教学大纲 课程名称：半导体器件物理 课程编号：M832001 课程学分：2 适用专业：集成电路工程领域 一、课程性质 本课程的授课对象为集成电路工程专业硕士研究生，课程属性为专业基础必修课。要求学生在学习过《电路分析》，《数字电路》，《模拟电路》和《半导体物理》的基础上选修这门课程。 二、课程教学目的 通过本课程教学，使得学生知道微电子学的用途、主要内容，明白学习微电子学应该掌握哪些基础知识；对微电子学的发展历史、现状和未来有一个比较清晰的认识；学会应用《半导体物理》的基础知识来对半导体器件物理进行分析，初步掌握电子器件物理、工作原理等基本概念，对微电子学的整体有一个比较全面的认识。

三、教学基本内容及基本要求 第一章微电子学常识 （一）教学基本内容 第一节晶体管的发明 1.1 晶体管发明的历史过程 1.2 晶体管发明对现代文明的作用 第二节集成电路的发展历史 2.1 集成电路的概念 2.2 集成电路发展的几个主要里程碑 2.3 目前集成电路的现状 2.4 集成电路未来发展的主要趋势 第三节集成电路的分类 3.1 集成电路的分类方法 3.2 MOS集成电路的概念 3.3 双极集成电路的概念 第四节微电子学的特点 4.1 微电子学的主要概念 4.2 微电子学的主要特点 （二）教学基本要求 了解：晶体管发明的过程，晶体管发明对人类社会的作用； 微电子学的概念，微电子学的特点； 掌握：集成电路的概念，集成电路发展的几个主要里程碑；集成电路的分

类方法，MOS集成电路的概念，双极集成电路的概念；第二章p-n结二极管 （一）教学基本内容 第一节p-n结的空间电荷区 1.1 p-n结的结构和制造概述 1.2 p-n结的空间电荷层和内建电场、内建电势 1.3 p-n结的耗尽层（势垒）电容 第二节p-n结的直流特性 2.1 p-n结中载流子的注入和抽取 2.2 理想p-n结的伏-安特性 2.3 实际p-n结的伏-安特性 2.4 大注入时p-n结的伏-安特性 2.5 实际p-n结的电流、正向结电压与温度的关系 第三节p-n结的小信号特性 3.1 p-n结的交流电流密度 3.2 扩散电容C d 第四节p-n结的开关特性 4.1 p-n结中少数载流子存储的电荷 4.2 p-n结的瞬变过程 4.3 p-n结反向恢复时间的计算 第五节p-n结的击穿特性 5.1 隧道击穿（Zener击穿）

现代半导体器件物理复习题

半导体器件物理复习题 1．简述Schrodinger 波动方程的物理意义及求解边界条件。 2．简述隧道效应的基本原理。 3．什么是半导体的直接带隙和间接带隙。 4．什么是Fermi-Dirac 概率函数和Fermi 能级，写出n(E) 、p(E) 与态密度和Fermi 概率函数的关系。 5．什么是本征Ferm 能级？在什么条件下，本征Ferm 能级处于中间能带上。 6．简述硅半导体中电子漂移速度与外加电场的关系。 7．简述Hall 效应基本原理。解释为什么Hall 电压极性跟半导体类型( N 型或P 型) 有关。 8．定性解释低注入下的剩余载流子寿命。 9．一个剩余电子和空穴脉冲在外加电场下会如何运动，为什么？ 10．当半导体中一种类型的剩余载流子浓度突然产生时，半导体内的净电荷密度如何变化？为什么？ 11．什么是内建电势？它是如何保持热平衡的？ 12．解释p-n 结内空间电荷区的形成机理及空间电荷区宽度与外施电压的关系。 13．什么是突变结和线性剃度结。 14．分别写出p-n 结内剩余少子在正偏和反偏下的边界条件。 15．简述扩散电容的物理机理。 16．叙述产生电流和复合电流产生的物理机制。 17．什么理想肖特基势垒？用能带图说明肖特基势垒降低效应。 18．画出隧道结的能带图。说明为什么是欧姆接触。 19．描述npn三极管在前向有源模式偏置下的载流子输运过程。 20．描述双极晶体管在饱和与截止之间开关时的响应情况。 21．画出一个n-型衬底的MOS 电容在积聚、耗尽和反型模式下的能带图。 22．什么是平带电压和阈值电压 23．简要说明p-沟道器件的增强和耗尽型模式。 24．概述MESFET 的工作原理。 25．结合隧道二极管的I-V 特性，简述其负微分电阻区的产生机理。 26．什么是短沟道效应？阐述短沟道效应产生的原因及减少短沟道效应的方法。 短沟道效应( shortchanneleffect )：当金属- 氧化物- 半导体场效应晶体管( MOSFE)T 的沟道长度L 缩短到可与源和漏耗尽层宽度之和(WS WD)相比拟时，器件将发生偏离长沟道 (也即L 远大于WSW D)的行为，这种因沟道长度缩短而发生的对器件特性的影响，通常称为短沟道效应。由于短沟道效应使MOSFET的性能变坏且工作复杂化，所以人们希望消除或 减小这个效应，力图实现在物理上是短沟道的器件，而在电学上仍有长沟道器件的特性。 当器件尺寸缩减时,必须将短沟道效应降至最低程度,以确保正常的器件特性及电路工作在器件按比例缩小设计时需要一些准则，一个简要维持长沟道特性的方法为将所有的尺寸及电压，除上一按比例缩小因素К (> 1)，如此内部电场将保持如同长沟道MOSFET 一般，此方法称为定电场按比例缩小(constant-field scaling) [ 随器件尺寸的缩减，其电路性能(速度以及导通时的功率损耗)得到加强§．然而，在实际的IC 制作中，较小器件的内部电场往往被迫增加而很难保持固定．这主要是因为一些电压因子( 如电源供 电、阈值电压等）无法任意缩减．由于亚阈值摆幅是无法按比例缩小的，所以，假若阈值电压过低，则关闭态（ off state ）（V G=0 ）的漏电流将会显著增加， 因此，待机功率（standby power）损耗亦将随之上升[12]．通过按比例缩小规范，