Testing & Measurement Speeds Design

Lab instruments are used for precise design verification, more accurate, reliable manufacturing outcomes

—by Larry Olson

Traditional design engineers originally started with a functional model on paper or in prototype to turn a design specification into the beginning of a real product. Analyzing this model involved using conventional techniques to confirm that the expected results could be achieved under the specified conditions. For a long time, reliability, quality, and even whether the product could actually be manufactured, were often estimated, assumed or simply overlooked.

Competition and consumer demands eventually forced designers to consider the importance of quality as well as performance, which brought into play such things as qualified supplier lists, and made quality, reliability testing and inspection in manufacturing much more important. In due time, design-for-manufacturing (DFM) was introduced to improve productivity on the production floor and reduce warranty costs and field failures/repairs.

Design & test departments merge

Early application of test and measurement principles, as well as extensive quality control inspection, involved establishing a lab-like environment in a separate QC (quality control) area. Often, quality assurance principles were applied to manufacturing under the theory that product quality would be assured in the same way that merely applying a new coat of paint would improve a product’s appearance.

As greater demands were placed on manufacturing with increasingly complex designs, and more advanced technology became available on the production floor, engineers came to recognize that quality control could no longer be assured by keeping it an isolated function, separate from the factory floor. One major innovation that resulted in a significant jump in productivity was the integration of customized QC activities and inspections with certain manufacturing processes. Another productivity boost came from instituting design-for-manufacturing concepts. Involving the design engineer in producing application solutions that were easier to manufacture brought the designer closer to production processes, producing better products overall.

Eventually, with the migration of more advanced test and measurement capabilities to the production floor, and design engineers becoming more involved in production processes and inspection instrumentation, the design/production cycle became more tightly coupled. Advanced technology was no longer the sole domain of scientists and specialists in the lab — design engineers began routinely using specialized, advanced tools in design verification and control of manufacturing processes.

Today, design engineers often function as test engineers, not only because of shrinking budgets in manufacturing, but also because instrumentation has been created that serves the design process directly. Also, as quality control and production testing continues to be integrated with manufacturing and production, there is an increasing need to verify designs earlier in the rollout cycle in terms of functionality details and manufacturability.

More advanced manufacturing technology, and greater precision required in parts construction and assembly, have meant tighter parts and system specifications as well as correspondingly more complex and precise measurement in manufacture. "Six-Sigma" quality programs require increased measurement precision for controlling processes more tightly. Also, adapting more sophisticated lab measurement instrumentation to the production line for operation by production personnel has required development of equipment features to factory floor training levels, while featuring settings and processing times that are more compatible with a production environment.

One added feature of this process has been that instrumentation development has enabled design engineers to make positive contributions to the development of test and measurement equipment itself. In the long run, this synergy has resulted in an accelerated cycle of advanced production that requires more advanced test and measurement instrumentation; and more advanced production, making higher-tech test equipment possible with greater, easier-to-use capability.

Test & measurement affects the market

"During the 1980s and into the 1990s, our company considered including a more balanced focus on its manufacturing customers," according to Chuck Cimino, business manager for emerging applications at Keithley Instruments, Solon, OH. "So, the company repositioned itself toward providing more solutions for emerging measurement applications." Many of these high-precision measurement applications are found in such industries as the manufacture of "mission-critical" components and sensors for use in airbag sensors and actuators, wireless devices, flat-panel displays, implantable electronic devices, magnetic and optical storage systems, advanced low-power RF semiconductor components, and a variety of other applications where precision settings are required in R & D and production tooling.

According to Cimino, "Many of Keithley’s test and measurements products were developed from customized solutions that started with items from our standard product line. These new products came about from Keithley engineers’ contact with end-users, our customers’ engineers and production people."

This increasing synergy between designers and manufacturing has accelerated the appearance of new products for customer applications. In the past, this process had occurred happened in the lab; but now there is an increasing need to be sensitive to the needs of the manufacturer and production, and even for the application product’s end-user.

One area where this change has been important, for example, has been the increasingly precise requirements of machining systems, and factory floor applications that require high-precision I-V curve tracing. Low-cost I-V source-measure units have been able to satisfy this need in the semiconductor industry.

Source-measurement equipment is designed to provide stimulus and measurement in low-current applications, high-precision I-V profiling, and general-purpose source and measurement instrumentation. "Keithley’s core technologies are based on the I-V measurement capabilities present in the company’s original products leveraged into the various systems for use in several different industries," Cimino reports, "with the common objective being precision electrical monitoring." In each of these areas, the objective has been the integration of measurement technology developed for lab situations with the system and automation requirements of increasingly precise, high-volume manufacturing technologies.

Although most industries benefited from these developments, they affected semiconductor products manufacturing the most of all. Some common products, such as air bag components, cell and mobile phones, and a number of PC components, would not be available today as cheaply as they are, and many of these would not be available at any price. Because of advanced test and measurement applications starting early in design and continuing throughout production, pocket PCs and PDAs (personal digital assistants), MP3 and DVD players, and a whole host of semiconductor-based assemblies are commonplace and extremely affordable today.

An example of this application in semiconductor devices production involves using photolithographic techniques to produce smaller and smaller structures, such as magnetic elements and IC surface features (transistor gates, etc.). Density increases have been at geometric and exponential rates, and with increased feature densities have come increased capacities, with correspondingly extreme reductions in cost and power requirements.

While geometries and power requirements have dropped, power densities have been maintained at relatively the same level. At the same time, the overall magnitudes of I-V measurements have dropped as well, requiring instruments to measure sub-picoamps instead of nano- and microamps in production settings, with much greater precision at higher speeds.

Application of high-tech design, supersensitive lab instruments to manufacturing has forced the modification and adaptation of these instruments for high-speed, precise measurement applications on the production floor. In the case of emerging low-K dielectric measurement in the semiconductor industry, it has required measurement of smaller and smaller I-V levels to properly profile dielectric characteristics. Creating the new processes for measuring adequately has required a closer working relationship between the manufacturing and research organizations within a company, as well as between companies having that culture as part of their history and orientation.

Technology advances set "roadmap" for future instrumentation

Products are now being optimized from their initial design through to production. Test and measurement instruments earlier found only in the lab are now being customized in their functionality and for ease-of-operation in in-line manufacturing testing applications. Many of the application areas in the semiconductor industry include wireless and optoelectronic devices, precision electronic devices in automotive and aerospace, and science and research situations.

Although adapting these advanced test and measurement technologies has been a limiting factor in development, Cimino notes that, "This step transforms the measurement capability in manufacturing by making more precise processing possible, as well as the ability to make more complex designs more precisely, cheaper, faster." Even so, with smaller physical and electrical parameter measurements being required, the demands of the production environment have reached beyond the laboratory in terms of manufacturing speed requirements, the number of measurements required (note: about the same number of parameters needed for profiling and regulation), and personnel training levels required. "Technology advances have laid out a ‘semiconductor roadmap’," says Cimino, "from the standpoint of capabilities and requirements in manufacturing these devices."

"Keithley reviewed the marketplace in manufacturing and lab requirements for about one year," says Cimino, "to determine those situations where lab-grade instrumentation would advance manufacturing technology." The result was the development of Keithley’s 2400-series of source-measure units (SMUs), including the SourceMeter family. Customer designers and engineers had adapted lab source measurement units for use on the manufacturing floor, responding to manufacturing demands for increased measurement throughput and settling time at production speeds. Since their release, increased production requirements have continued to steer Keithley’s SMU development.

Keithley’s SourceMeter line of precision, high-speed I-V characterization instruments is used manually in basic and applied research for new materials, devices, and processes. These units are used both manually and semi-automatically in R & D, design validation engineering and in-line production testing. The core measurement technologies have been designed into bench and system semiconductor characterization systems that are used for research, development, and production testing of advanced, low power, and RF high-speed integrated circuits. They also have been used in TFT LCD characterization and production process monitoring.

For more information:
Keithley Instruments,
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