Electronic coupling is the transfer of energy from one circuit or medium to another. Sometimes it is intentional and sometimes not (crosstalk). I hope that this column, by mixing technology and general observations, is thought provoking and “couples” with your thinking. Most of the time I will stick to technology but occasional crosstalk diversions may deliver a message closer to home.
Testing the Supply Chain
Much the same as the world, test is not simply black or white but varying shades of grey and a jumble of colors. Test has continually responded to semiconductor technology challenges to provide the right solutions. As a result, the organizational placement and “supply chains” for test have rarely been Continue reading “Coupling & Crosstalk: Testing the Supply Chain”
In an effort to reduce the cost-of-test (COT), a number of customers are increasing the parallelism of logic wafer probe cards. However, due to the complexity such as pitch and number of probes, the pricing for these cards is reaching astronomical levels. We do not believe this trend is sustainable, let alone logical. The presentation suggested examples of alternative solutions. It is clear that critical solutions need to be optimized at the test cell, factory, and supply chain level not just at the consumable (probe card) level.
Wow! The Burn-in and Test Strategy (BiTS) Workshop just turned 15! The world of semiconductors has certainly changed over the years. And the BiTS Workshop has kept up with what is “Now & Next” in the burn-in and test of packaged integrated circuits (ICs). These achievements were celebrated in style by the more than three hundred participants at the recently held 2014 BiTS Workshop in Mesa, Arizona.
Attending the SEMIIndustry Strategy Symposium (ISS) is like drinking from a fire hose with the additional risk of whiplash. Don’t get me wrong, it is an exquisite fire hose but sometimes the data presented can be overwhelming at this conference of semiconductor supply chain executives. The majority of the attendees and presenters are executives from the SEMI member companies that develop the equipment, materials, processes, and technology used to build, test, and package semiconductors. And the executives present from the semiconductor manufacturers are typically the “end customers”.
The greatest value of SEMI ISS, beyond the networking, is the strategic overview of the entire semiconductor ecosystem. What are the market drivers, the technology needed, and the roadmap status of this industry? It is true that we all know where we need to head courtesy of Moore’s Law and the International Technology Roadmap for Semiconductors which attempts to keep us on that trajectory. The pressure of consumers needing wanting greater functionality at lower costs is relentless. Much of the technological detail of this ecosystem is addressed in a myriad of other forums throughout the year. ISS ties these technical requirements, development needs, and business needs back to the strategic direction and desires of the global marketplace.
As the number of probes on probe cards increase due to greater parallelism, driven by the desire for one touchdown testing and the future transition to 450 mm wafers, the total force required to probe a wafer increases if there is no reduction in the force per probe. This wafer prober chuck needs to apply the required force by pushing the wafer against the probe card typically held in place by the structure of the prober. With 200K probes on a 450 mm wafer each requiring 5 gF this is approximately equal to 1 ton (2205 lbF) of applied force. To reduce these force requirements wafer chuck and prober structure, Advantest and JEM have Continue reading “IEEE Semiconductor Wafer Test Workshop 2012 – Session 5 (Tuesday)”
As the final presenter at this week’s IEEESemiconductor Wafer Test Workshop (SWTW), I outlined how critical it is to understand the true cost of a product’s architecture in “Probe Card Cost Drivers from Architecture to Zero Defects“. Without a proper understanding of these costs – especially for fully custom high technology products such as wafer test probe cards – it is impossible to maintain a sufficient gross margin. Gross margin is essential to maintain the health of a company and to fund the research & development required for innovation.
Yes, there were a few in the audience who appeared pleased since they are confident that their products are on the right path. There were others who may have been upset based upon their company’s direction. I would argue that a proper diagnosis – regardless of how disturbing – is essential to drive the proper cure.
There is plenty of opportunity in the test market and reasons for optimism. The key to long term prosperity is to really understand the fundamentals of the business and not be blinded by the technology.
I thank those who stayed for the entire conference and welcome your thoughts below. And I will be posting more about the conference (including my summaries) in the next few weeks.
Starting off something new is often challenging and difficult with many unknowns. Kudos to Nick Langston for creating the Silicon Valley Test Conference that was held last week. (November 8 & 9, 2010) It was the first test conference to actually take place in Silicon Valley. And yes there were some minor “bugs” like registration delays and a no-show by the audio visual contractor that should be solved in next year’s Rev 2.0. Even with a few rough edges, the quality of the presentations and the exhibitors shined through to make this a success.
Jay Thomas, Grund Technical Solutions, LLC., “Probe Cards with Modular Integrated Switching Matrices”:
For the last 30 years, most scribeline parametric testing has been approximately 85% Current-Voltage (I-V) testing and 15% Capacitance-Voltage (C-V) testing. For these types of tests a 10 MHz bandwidth switch matrix has been sufficient.
However, some of the larger fabs such as HP, IBM, and Intel have started performing pulsed Current-Voltage (PIV) and electrostatic discharge (ESD) testing. These customers started this type of testing about four years ago unknown to Agilent & Keithley (the two largest DC parametric tester suppliers). This PIV and ESD testing requires high frequency switch matrices with 1 GHz bandwidth. [For more about ESD testing please see Jay’s second presentation below in this session.] Continue reading “IEEE Semiconductor Wafer Test Workshop – Parametric / Scribeline Probing – Session Six (Tuesday)”
Mark McLaren, Integrated Technology Corporation, “Metrology Solutions for Very Large Probe Cards”:
Over the past few years as the number of memory devices to be tested in parallel has increased so has the size of probe cards to support this multisite testing. A few years ago memory probe cards grew to 440 mm diameter and recently they increased to 480 mm diameter. Now a similar growth in size has been seen for non-memory applications. Even though the parallelism (number of devices to be tested at once) has increased (but not on the scale of memory parallelism), the size increases have been the result of pushing more testing from package test to wafer test. These additional tests have required more local test resources (circuitry close to the device being tested) which require more real estate on probe cards. Continue reading “IEEE Semiconductor Wafer Test Workshop – Standards and Methods – Session Four (Monday)”
The 20th annual IEEE Semiconductor Wafer Test Workshop (SWTW) started this evening. Rumor has it that attendance is over 240 this year which is a vast improvement over last year’s 160 or so attendees. At the peak the conference had almost hit 600. Things started off well with a reception where I had the chance to catch up with many industry friends and colleagues.
Balancing test coverage versus test cost. What does a test failure mean? Value of yield increase
… and how it impacts your bottom line!
A poorly implemented semiconductor test cell may pass integrated circuit (IC) parts that are either defective or have marginal performance. They can cause the electronic devices in which they will be assembled to either malfunction or completely fail. However, two other conditions require evaluation. Having false negative test “escapes” is expensive in terms of final product test failures, warranty costs, customer dissatisfaction, etc. In turn, the false positive test escapes needs to be balanced against the cost of false negative failures where otherwise good parts fail the tests and are discarded. Test engineers, product managers, quality engineers, and operational managers needs to make either implicit or explicit decisions as to the proper balance in adjusting the test limits. The goal is to cost effectively approach “zero defects” without “throwing out the baby with the bath water”.
A test process generally categorizes the item or device being tested as “pass” or “fail”. Sometimes passing devices are graded (typically by speed or other desired quality) and failing devices are often grouped by failure mode. “Coverage” is how well a particular test process measures the functionality and specifications of a given device. If every feature and specification is tested then it is said to have 100% test coverage. However, exhaustive testing is usually expensive due to long test times which translates in to operational costs including the depreciation of the test system and greater test setup complexity (equipment and development cost). Sometimes complete coverage is not possible or practical so there needs to be a trade-off between coverage and cost.