Semiconductor manufacturing consists of a series of sequential process steps in which layers of materials are deposited on substrates, doped with impurities, and patterned using photolithography to produce ICs. Figure 1.6 illustrates the interrelationship between the major process steps used for IC fabrication.
Polished wafers with a specific resistivity and orientation are used as the starting material. The film formation steps include thermally grown oxide films, as well as deposited polysilicon, dielectric, and metal films. Film formation is often followed by photolithography or impurity doping. Photolithography is generally followed by etching, which in turn is often followed by another impurity doping or film formation. The final IC is made by sequentially transferring the patterns from each mask, level by level, onto the surface of the semiconductor wafer.
Figure 1.6. Flow diagram for generic IC process sequence.
After processing, each wafer contains hundreds of identical rectangular chips (or dies), typically between 1 and 20 mm on each side, as shown in Figure 1.7a. The chips are separated by sawing or laser cutting; Figure 1.7b shows a separated chip.
Figure 1.7. (a) Semiconductor wafer; (b) IC chip; (c) MOSFET and bipolar transistor.
Schematic top views of a single MOSFET and a single bipolar transistor are shown in Figure 1.7c. Inserted into this process sequence are various points at which key measurements are performed to ensure product quality.
This is an excerpt from
Fundamentals of Semiconductor Manufacturing and Process Control by Gary S. May and Costas J. Spanos
A practical guide to semiconductor manufacturing from process control to yield modeling and experimental design. Fundamentals of Semiconductor Manufacturing and Process Control covers all issues involved in manufacturing microelectronic devices and circuits, including fabrication sequences, process control, experimental design, process modeling, yield modeling, and CIM/CAM systems. Readers are introduced to both the theory and practice of all basic manufacturing concepts.
Following an overview of manufacturing and technology, the text explores process monitoring methods, including those that focus on product wafers and those that focus on the equipment used to produce wafers. Next, the text sets forth some fundamentals of statistics and yield modeling, which set the foundation for a detailed discussion of how statistical process control is used to analyze quality and improve yields.
The discussion of statistical experimental design offers readers a powerful approach for systematically varying controllable process conditions and determining their impact on output parameters that measure quality. The authors introduce process modeling concepts, including several advanced process control topics such as run-by-run, supervisory control, and process and equipment diagnosis.
Critical coverage includes the following:
• Combines process control and semiconductor manufacturing
• Unique treatment of system and software technology and management of overall manufacturing systems
• Chapters include case studies, sample problems, and suggested exercises
• Instructor support includes electronic copies of the figures and an instructor's manual
Graduate-level students and industrial practitioners will benefit from the detailed examination of how electronic materials and supplies are converted into finished integrated circuits and electronic products in a high-volume manufacturing environment.
Reader W Boudville says, "For those of you working in a fab, or designing processes to be used in it, May gives a good summary of what is generally known and non-proprietary. He explains the key steps in photolithography, wet and dry etching, the different ways to dope, and deposition processes.
But along with these steps, every fab needs to monitor them for quality control. So we get discussions of how to measure data about a wafer. Like using inteferometry or ellipsometry to measure the thickness of a deposited thin film. Or using a four point probe for capacitance or resistance measurements.
A lot of the text also deals with statistics and how to maximise your device yield. Involves numerous modelling choices and process controls.
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