Metrology characterisation
Broad spectrum analysis
Keithley Instruments recently launched an electrical characterization tool that provides a broad spectrum of applications across semiconductor manufacturing. David Ridsdale spoke to Keithley’s marketing director, Mark Cejer, about the capability and application of the new tool.
Q
Keithley has introduced a new tester for high end semiconductor activities such as LEDs, interconnects and high power semiconductors. Testing is an important part of manufacturing but many manufacturers see it as an annoying additive. However, an increasing complexity and lack of visual ability has seen such testing become more important. Do you think testing has moved from an added value to an enabling process for future needs?
A
It’s long past time for device manufacturers to start thinking about test as much more than “a necessary evil.” The growing demand for higher efficiency semiconductors is driven in part by the push for more energy-efficient devices. One of the goals for end products that employ lots of power semiconductors, such as power supplies for servers, for example, must be reducing their energy consumption. When the power supply is in standby/off mode, leaky semiconductors in the inputs will waste a lot of electricity, especially when that leakage is multiplied by the number of power supplies in a big server farm. To improve energy efficiency, IC manufacturers are constantly exploring ways to create more efficient silicon devices, as well as those based on compound semiconductors like silicon carbide and gallium nitride, which are inherently more efficient than silicon. All of that means greater testing challenges: “more efficient” means materials and devices that are less leaky, “less leaky” means IC makers need to be able to characterize ever-lower leakage currents, which is especially challenging in production. Older instrumentation, designed for characterizing relatively leaky silicon, typically just is not up to the challenge. The ability to characterize power semiconductors with pulsed measurements is also critical to ensuring
accuracy because pulsed measurements let you test using high current levels without creating the self-heating problems that would occur if you were sourcing high DC currents. High brightness light emitting diodes (HBLEDs) also present some critical testing challenges. These devices are increasingly in demand for use in applications like backlighting displays, automotive headlamps, solid-state lighting that goes on buildings, and dozens of others. For these types of applications, the color of the light they output must be highly consistent from device to device because they’re typically packaged with multiple LEDs in a module and multiple modules in a single end product. Any significant color variation is immediately obvious and would be unacceptable to the consumer. Ensuring high color consistency requires the ability to test these devices with extreme accuracy. Here, too, high throughput pulse testing is essential because HBLEDs are very susceptible to self-heating, which will affect the color of the light they output. And, of course, in production, test throughput is equally critical. And those are the big issues the Model 2651A High Power System SourceMeter instrument was designed to address.
Q A
Many companies highlight the generic capacities of their tools but with this tool Keithley have focused on the specialities. What motivates such a decision and what advantages does it provide the manufacturer?
For some of our customers, all we have to
say is “We’ve got a terrific new 50A SMU” and they’ll know exactly how to use it in their applications. But for the rest, we feel that test vendors have a big responsibility to their customers to help them choose and use their
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www.euroasiasemiconductor.com Issue IV 2011
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