GaNReliability Report2018

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GaN-on-Silicon Reliability and Qualification Report

A summary analysis of application-specific stress testing

methodologies and results demonstrating the reliability of Gallium

Nitride on Silicon (GaN-on-Si) RF power transistors for commercial

wireless basestation infrastructure

INTRODUCTION The performance and reliability benefits of GaN-on-Si for RF and microwave applications have been well documented since the 2006 qualification of first-generation GaN-on-Si technology for volume deployment into military and defense applications. With millions of GaN-on-Si RF transistors shipped to date, the multi-generation maturation of GaN-on-Si technology has opened the door to its mainstream commercial deployment in 4G LTE and 5G wireless basestation infrastructure, and onward to solid-state RF energy applications spanning cooking, lighting, automotive ignition and beyond. The qualification methodologies employed for GaN-on-Si technology are similarly mature, informed by decades of industry standardized testing of silicon-based devices. The comprehensive testing data gathered on GaN-on-Si-based RF power transistors over multiple generations of GaN-on-Si fabrication shows a marked progression in key metrics centric to device performance and reliability.

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TESTING METHODOLOGIES FOR BASESTATION APPLICATIONS The stringent reliability requirements for wireless basestations invite equally stringent RF device testing methodologies designed to account for harsh environments and operating conditions characterized by extreme temperature, humidity and voltage variances. Perhaps counterintuitively, reliability testing methodologies for RF devices targeting wireless basestations are often times more exacting than the testing required for many military and defense applications. This owes in large part to the inherent cost pressures on commercial wireless infrastructure. Whereas military-grade RF systems may employ advanced and/or labor-intensive component packaging techniques to boost overall reliability and robustness, these techniques are cost prohibitive for volume-scale 4G LTE and 5G wireless basestation manufacturing processes. Amid these constraints, it’s imperative that GaN-on-Si-based RF power transistors are optimized for the highest levels of reliability to help ensure continuous, long-lifecycle basestation operation on par with modern military communications infrastructure. This report provides an overview of the testing methodologies used to assess the reliability of current-generation GaN-on-Si-based power transistors for wireless basestations, and shows the resulting test data. The tests described here – spanning Highly Accelerated Stress Tests (HAST), High Temperature Operating Life (HTOL), High Temperature Reverse Bias (HTRB), and Accelerated Life Testing (ALT) – augment previously performed, routine testing for Intermittent Operating Life (IOL), Temperature Cycling, Mechanical Shock and Vibration, Destructive Physical Analysis (DPA), and Electrostatic Discharge (ESD) testing. HIGHLY ACCELERATED STRESS TESTS (HAST) RF transistors deployed in the field for wireless basestation infrastructure need to be robust against a variety of environmental stresses that could induce RF component failures, including elevated temperatures, temperature cycling through hot and cold conditions, and high humidity conditions. MACOM’s HAST testing is intended to simulate a 20 year system lifetime in 96 hours of intensive stress testing, utilizing JEDEC JESD22-A110 testing procedures. HAST testing on current-generation MACOM GaN-on-Si power transistors was performed at 130oC and 85% relative humidity in a pressurized chamber for sustained moisture capture. These tests were performed on more than 75 samples sourced from 4 separate manufacturing lots to confirm test result repeatability. Each part was tested for datasheet specification conformance prior to HAST testing, and re-tested after HAST to demonstrate sustained spec conformance. MACOM GaN-on-Si-based power transistors

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met HAST qualification requirements in every testing instance. The figure below exhibits the stability of RF power performance for a representative subset of the parts subjected to this harsh stress test.

HIGH TEMPERATURE OPERATING LIFE (HTOL) With HTOL testing, RF transistor are biased in the DC conditions representative of the end application and subjected to maximum operating temperatures for 1,000 continuous hours as specified by JEDEC JESD22-A108 testing procedures. Successful testing affirms datasheet specification conformance, with the goal of zero failures. MACOM tested over 231 samples of 550W GaN-on-Si RF power devices, and successfully met the requirements of the basestation market, as shown in the data below. Each part was biased at a drain voltage of 50V and drain current of 1.2A, leading to channel temperatures exceeding 225°C for the duration of the test. As was seen in HAST, the graph below shows minimal change in RF power performance after the HTOL test.

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HIGH TEMPERATURE REVERSE BIAS (HTRB) HTRB testing is similar in nature to HTOL, except that the supplied electrical voltage characterizes the device in its ‘off’ state. This testing is designed to assess the voltage breakdown behavior of the device, following the approach described in MIL-STD 750, test method 1026. During this test, drain and gate voltages of 100V and -6V, respectively, were applied to more than 100 devices from 3 manufacturing lots during 1,000 hours of thermal stress at 150°C. Each part was tested for datasheet specification conformance prior to testing, and re-tested after to demonstrate sustained spec conformance. MACOM GaN-on-Si-based power transistors met all HTRB qualification requirements—all parts remain spec compliant as evidenced by the graph shown below.

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ACCELERATED LIFE TESTING (ALT) The goal of ALT is to stress devices in order to observe the manner in which they eventually degrade and fail. By analyzing the types of failures and the timing at which they occur, testers can more accurately predict the evolution of device performance under realistic application conditions for operating temperature and applied voltages/operating bias.

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Image 1: An Automated Accelerated Reliability Test System (AARTS) deployed in

MACOM’s testing lab, with capacity for 60 devices

Image 2: A top-down view of the test fixtures within the AARTS

Image 3: A close-up view of an AARTS test fixture, including input/output matching circuit boards

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For these tests, MACOM GaN-on-Si power transistors were operated at 50V drain voltage and drain current of 80 milliamps per millimeter, producing thermal dissipation of 4W per millimeter of DC power. To show reliable operation at maximum operating channel temperatures of up to 225oC, MACOM performed ALT testing at temperatures between 300 and 355oC. The extrapolated data of these tests prove that MACOM’s GaN-on-Si RF power transistors far exceed challenging basestation market requirements of 107 hours (1,000 years) at 225oC. As shown in the Arrhenius plot below, MACOM’s GaN-on-Si devices support operational lifetimes of over 108 hours, representing a mean time to failure (MTTF) of over 10,000 years.

CONCLUSION GaN-on-Si-based RF power transistors targeted for 4G LTE and 5G basestation infrastructure must adhere to, uphold and outperform the rigorous reliability testing standards achieved with legacy semiconductor technologies. Comprehensive testing of MACOM’s GaN-on-Si RF power transistor technology has clearly demonstrated this capability, exceeding current LDMOS 10th generation performance. Looking forward as basestation, RF energy and other RF market requirements become more demanding, MACOM is already developing next generation GaN technologies to continue to meet and exceed those expectations, including higher frequency, higher power, and higher efficiency.

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With over 50 years of proven industry leadership in delivering reliable semiconductor technologies to mainstream commercial markets, MACOM has again affirmed its commitment to powering the most demanding RF and microwave applications. For more information about MACOM’s GaN-on-Si technology, visit www.macom.com/gan

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