1、1,Batch Processing Definition, Advantages, Disadvantages,A sequence of one more steps (recipe) usually carried out in more than one vessel and in a defined order, yielding a finished product Production amounts are usually smaller than for continuous processing Requires reduced inventories and shorte
2、r response times Final product quality must be satisfied with each batch (no blending) More emphasis on production scheduling in batch processing,2,Other Advantages,Batch time can be adjusted to meet quality specs Repetition is conducive to continuous improvement in product Slow dynamics permit real
3、-time calculations Greater agility,3,4,Batch Processing Used in Manufacturing,Electronic materials Specialty chemicals Metals Ceramics Polymers Food and agricultural materials Biochemicals Multiphase materials/blends Coatings Composites,5,Representative processing steps in a semiconductor wafer fab
4、(Deposition, Patterning, Etching, Doping, etc),6,Unit operations in microelectronics manufacturing are characterized by:,Physical/chemical complexity Inability to measure directly many process variables High sensitivity to process changes Multiple inputs/multiple outputs,7,CD Variation Effects in Pa
5、ttern Transfer,Wafer,Flatness Reflectivity Topography,Resist,Reticle,Temperature Uniformity Time Delay,Aberrations Lens Heating Focus Leveling Dose,CD Defects Edge Roughness Proximity Effects,Stepper,Time Temperature Dispense Pattern Rinse,Refractive Index Thickness Uniformity Viscosity Contrast,PEB
6、,Develop,Power Pressure Flow rates,Etch,Amines Humidity Pressure,Environment,8,Silicon Integrated Circuit Technology Roadmap,9,Comparative Economics,Revenue/Capital1Chemical & Petrochemical 22.4Pharmaceutical 19.6Semiconductor 6.8Capital productivity is a major driving force for semiconductors _ 1Fr
7、om 1997 US Census Bureau,10,Why Control Critical Dimension (CD)?,Small changes in CD distribution = Large $ values lost,290,11,Figure 19.1 The five levels of process control and optimization inmanufacturing. Time scales are shown for each level.,12,Control Hierarchy in Batch Processing,Sequential co
8、ntrol to step the process through a recipe Logic control to deal with device interlocks Within-the-batch control to make set point changes and reject disturbances Run-to-run control to meet final quality constraints Batch production control to maximize utilization of equipment and minimize cycle tim
9、e,13,Batch Mixing Tank-Operations Sequence,Introduce liquid A until level reaches LH2 Close A valve, open B valve and start mixer When level reaches LXH2, stop flow of B and the mixer and open discharge valve (VN9) Discharge product until level reaches LL2, then close the discharge valve.,14,Figure
10、22.7,15,Graphical Description of Batch Sequence,Information flow diagram Sequential function chart Binary logic diagram Ladder logic diagram,16,Figure 22.8,17,Within-the-Batch Control: Operational Challenges,Time-varying process characteristics (no steady state) Nonlinear behavior Model inaccuracies
11、 On-line sensors often not available Constrained operation Unmeasured disturbances Irreversible behavior,18,19,Time 10 sec Figure 3. Definition of bring-in (Rapid Thermal Processing),1000CTemperature0,20,Run-to-Run (RtR) Control,Keeps batch process product on target by using feedback to manipulate b
12、atch recipe for consecutive batches Required due to a lack of in situ, real-time measurements of product quality of interest Extremely useful where initial conditions or tool states are variable and unmeasurable Supervisory controller determines optimal setpoints for real-time control loops (typical
13、ly PID),21,RtR Control,Predominantly used in semiconductor and batch chemical industries Can be viewed as discrete-time process (k, k+1, k+2 vs. t) Good for treating drifting processes (e.g. reactor fouling) Run-to-run optimization can be performed using process model Integrates with fault detection
14、,22,Use of RtR Control,Examples of events which can have slow dynamics or infrequent step changes- equipment aging- periodic machine maintenance- changes in feedforward signal- measure disturbance- major fault, such as instrumentationdegradation,23,Application: Resist etch process,The incoming patte
15、rn is masked with linewidths greater than required. An additional step is added to the etch process which etches the resist pattern. The resist etch step trims the lines to the proper resist linewidth. The rest of the etch transfers the resulting mask pattern into the polysilicon, creating the poly
16、gate structures.,Linewidth,24,Results Increased Cpk,25,Reduction in STI Rework with RtR,26,Figure 22.19 Batch control system a more detailed view,27,Characteristics of batch scheduling and planning problems (Pekny and Reklaitis),DETERMINEWhat Product amounts: lot sizes, batch SizesWhen Timing of spe
17、cific operations, run lengthsWhere Sites, units, equipment itemsHow Resource types and amounts,GIVENProduct requirements Horizon, demands, starting and Ending inventoriesOperational steps Precedence order Resource utilizationProduction facilities Types, capacitiesResource limitations Types, amounts,
18、 rates,28,Welcome to the Real World!,For a real lot in a real fab, there are: Reworks Different process equipment at previous steps WIP ordering/processing Equipment/Consumable material changes Recipe changes/adjustments Scheduled/Unscheduled maintenance Multiple reticle instances Engineering lots,2
19、9,Figure 22.17 Multiproduct batch plant,30,Multi-Product Processing Overview,Fab Tool,Process 2,Fab Tool,Process 1,Process 2,Fab Tool,Process 1,Process 1,Multi-product / Single Process,Single Product / Multi-process,Multi-product / Multi-process,31,Metrology Variations,Process,Correct Metrology Ordering,Incorrect Metrology Ordering,Incorrect Metrology Ordering,
