Batch processes electronic materials

The fabrication of microelectronic and photonic components involves long sequences of batch chemical processes. The manufacture of advanced microstructures can involve more than 200 process steps and take from 2 to 6 weeks for completion. The ultimate measure of success is the performance of the final circuits. The devices are highly sensitive to process variations and are difficult, if not impossible, to repair if a particular chemical process step should fail. Furthermore, because of intense competition and rapidly evolving technology, the development time from layout to final product must be short. Therefore, process control of electronic materials processing holds considerable interest [30, 31]. The process control issues involve three levels ... 

Usually, for the production of small quantities of high-priced chemicals, such as in th manufacture of pharmaceuticals, foods, electronic materials, and specialty chemicals, batch fed-batch, and batch-product removal processes are preferred. This is often the case in bio processing, for example, when drugs are synthesized in a series of chemical reactions, eacl having small yields, and requiring difficult separations to recover small amounts of product This is also the case for banquet facilities in hotels, which prepare foods in batches, and fo many unit operations in the manufacture of semiconductors. As discussed in Chapters 3 am 4, these processes usually involve a recipe, that is, a sequence of tasks, to be carried out h various items of equipment. In the latter sections of this chapter, variations on batch proces schedules are discussed, as well as methods for optimizing the schedules. 

Batch processing is widely used to manufacture specialty chemicals, metals, electronic materials, ceramics, polymers, food, biochemicals and pharmaceuticals, multiphase materials/blends, coatings, and composites, an extremely broad range of processes and products. The unit operations in batch processing are also quite diverse, and some are analogous to operations for continuous processing. 

Figure 12.5 A schematic diagram of some of the major elements of a typical low-pressure chemical vapor deposition system. Note that the entire process is typically contained within a safety enclosure because many of the reactants as process gases are either flammable or toxic. A toxic gas detector scans the interior of the enclosure, especially around the gas piping, for leaks. The scrubber reacts the source materials that are left over after passing through the reactor tube to render them harmless. Typically the valves for all sources are operated electronically so that the user does not need to open the safety enclosure except to load substrates on the susceptor. The system shown here includes a single substrate on a tilted susceptor. Batch processes are similar except in the arrangement of substrates in the reactor tube. Other reactor tube designs are also used. More specific reaction examples are given in Section 12.8.

Examples of GxP processes (functions) include supplier management, procurement, goods receipt, materials management, production control, quality control, batch release, distribution, recall, customer complaints, batch tracking, and compliance management (e.g., SOP management, electronic data archiving). 

Batch Record IQA (1994) Documents (including those stored in photographic and electronic form) that record stages in the manufacture of a batch, details of ingredients and process equipment used, methods followed, in-process controls carried out, test results obtained, dates of manufacture, and testing and history of the storage of the pharmaceutical raw material. 

This reaction has been modified by Alder and Longo by heating the mixture of pyrrole and aldehyde in propionic acid at 4 °C while open to air to give unhindered porphyrin derivatives. However, such modification often causes problems such as the formation of a high level of tar material that complicates the purification process, the incompatibility with certain functional groups on aldehydes, and the low batch-to-batch reproducibility. On the other hand, Lindsey has carried out the reaction in the presence of a catalytic amount of BF3 or TFA under equilibrium conditions, followed by oxidation with an electron-deficient quinone, such as DDQ. " In addition, this reaction has been extended to the preparation of corrole by the application of an excess amount of pyrrole. ... 

Other film dosimeters. Colorless PVC foils are used at electron accelerators to monitor the irradiation process and the accelerator parameters (like scan width and beam spot). In these materials unsaturated chemical bonds form upon irradiation and the optical absorption of these new species can be measured by spectrophotometry at 395 nm in the dose range of 0.5-60 kGy (Artandi and Stonehill 1958). It is important to mention, however, that due to various factors (environmental effects on the response, dose rate effects, batch-to-batch variation, etc.) these films should not be considered and used as dosimeters, but only as dose indicators. 

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