Reliability Testing Acceleration Testing
Most semiconductor devices have lifetimes that extend over many years at normal use. However, we cannot wait years to study a device; we have to increase the applied stress. Applied stresses enhance or accelerate potential fail mechanisms, help identify the root cause, and help labcompanion take actions to prevent the failure mode.
In semiconductor devices, some common accelerants are temperature, humidity, voltage, and current. In most cases, the accelerated testing does not change the physics of the failure, but it does shift the time for observation. The shift between accelerated and use condition is known as ‘derating.’
Highly accelerated testing is a key part of JEDEC based qualification tests. The tests below reflect highly accelerated conditions based on JEDEC spec JESD47. If the product passes these tests, the devices are acceptable for most use cases.
Temperature Cycle
Per the JESD22-A104 standard, temperature cycling (TC) subjects the units to extreme high and low temperatures transitions between the two. The test is performed by cycling the unit's exposure to these conditions for a predetermined number of cycles.
High Temperature Operating Life (HTOL)
HTOL is used to determine the reliability of a device at high temperature while under operating conditions. The test is usually run over an extended period of time according to the JESD22-A108 standard.
Temperature Humidity Bias/Biased Highly Accelerated Stress Test (BHAST)
According to the JESD22-A110 standard, THB and BHAST subject a device to high temperature and high humidity conditions while under a voltage bias with the goal of accelerating corrosion within the device. THB and BHAST serve the same purpose, but BHAST conditions and testing procedures enable the reliability team to test much faster than THB.
Autoclave/Unbiased HAST
Autoclave and Unbiased HAST determine the reliability of a device under high temperature and high humidity conditions. Like THB and BHAST, it is performed to accelerate corrosion. Unlike those tests, however, the units are not stressed under a bias.
High Temperature Storage
HTS (also called Bake or HTSL) serves to determine long-term reliability of a device under high temperatures. Unlike HTOL, the device is not under operating conditions for the duration of the test.
Electrostatic Discharge (ESD)
Static charge is an unbalanced electrical charge at rest. Typically, it is created by insulator surfaces rubbing together or pulling apart; one surface gains electrons, while the other surface loses electrons. The result is an unbalanced electrical condition known as static charge.
When a static charge moves from one surface to another, it becomes Electrostatic Discharge (ESD) and moves between the two surfaces in a form of a miniature lightning bolt.
When a static charge moves, it becomes a current that can damage or destroy gate oxide, metal layers, and junctions.
JEDEC tests ESD in two different ways:
1. Human Body Mode (HBM)
A component level stress developed to simulate the action of a human body discharging accumulated static charge through a device to ground.
2. Charged Device Model (CDM)
A component level stress that simulates charging and discharging events that occur in production equipment and processes, per the JEDEC JESD22-C101 specification.
