The 2015 revision of the Test Technology Roadmap identifies many significant changes to the industry as well as a number of significant challenges which the industry is working to overcome.
1. Notable Changes
a. Cost-of-Test – Reducing the cost-of-test, while always an industry goal, has begun to suffer from diminishing returns when looking at the traditional approach such as capital cost reduction or site count increases. As part complexity increases, test times and thus cost-of-test has also been increasing and driving up the cost-of-test. Additionally, the cost of "consumable" test interface material has come to play a much larger role in cost-of-test. Interestingly, the overall cost-of-test is becoming a lower percentage of the overall IC manufacturing expense while at the same time test is having a greater impact on profitability.
b. Heterogeneous Integration – As more and more 2.5D and 3D device integrations come on the market it has become clear that additional testing is necessary to avoid scrapping expensive sub-assemblies.
c. Wafer probing – After reporting big changes in probe pitch and counts in 2013, we once again need to adjust the requirements in 2015. These changes are largely in response to the broad deployment of microbumps and pillar type interconnects which drive up the density and down the pitch.
d. Logic Table – The product groupings have changes with this publication. The new groupings are:
- i. MPU-HP (Big Data) – High Performance MPU (MPU,Servers, GPU)
- ii. MPU-CP (Mobile) – Mobile Consumer MPU (SOC, APU)
- iii. SOC-CP (Low power Devices) – Low-Power Consumer (MCU, IoT, MEMs, Analog)
This product grouping was chosen to provide a better alignment with the ITRS 2.0 documents. An additional benefit of this grouping is it provides a better understanding of the challenges in the testing of low power devices . Areas with Significant Challenges for the Future:
a. Thermal – Various needs are pushing the performance envelope for high-performance thermal solutions both at wafer probe as well as in a packaged device environment. More sophisticated automotive electronics demand testing to a wider temperature range. In addition, long test times are pushing scan speeds up resulting in a need for better device cooling during test.
a. Adaptive Device Testing – This technique continues to deliver significant value to the industry. Looking forward this technology is challenged to broadly implement real-time feed forward and feedback systems in an industry which has increasingly complex supply chains. Adaptive test may prevent an increase in test cost.
b. Parallel Testing – The typical parallel testing site counts for most products are not changing. With the increased device complexity this is one of the driving forces in an increasing cost-of-test. Areas where the industry is working are to increase parallel site counts are RF device testing, LCD testing, and MEMs device testing.
c. Logic Device Testing – With the broad deployment of FinFET technology the complexity of digital devices continues to increase. Further enhancing this trend is the trend toward heterogeneous integration. While pattern compression techniques help manage the challenge of test data volume it does little to help reduce test times and hence cost of testing.
d. Optical Interface Testing – In 2015 we are starting to see a trend toward the use of optical interfaces in the high-speed SerDes area. Testing optical device brings with it big challenges for precise fiber alignment as well as new test methods when working with light as a signal source.
Challenges and changes in the other topic areas are less dramatic.