How to conduct reliability testing of IGBT?
INDUSTRIAL LCD DISPLAYS / IGBT MODULES DISTRIBUTOR

Infineon / Mitsubishi / Fuji / Semikron / Eupec / IXYS

How to conduct reliability testing of IGBT?

Posted Date: 2024-01-18

In today's semiconductor market, two important factors for a company's success are product quality and reliability. The two are interrelated, and reliability is reflected in long-term quality performance over the expected life of the product. For any manufacturer to remain in business, it must ensure that its products meet or exceed basic quality and reliability standards. As a semiconductor supplier, ON Semiconductor provides products that can operate in harsh environments for demanding applications and achieve high quality and reliability.

It was recognized that the best way to achieve guaranteed quality performance was to abandon the previous "quality by testing" approach and instead embrace the new "quality by design" philosophy. At ON Semiconductor, we use a dual approach to achieve the ultimate level of quality and reliability. First, we develop and implement a set of inherently reliable processes. We then meticulously adhere to process specifications every step of the way from start to finish. Develop and implement inspections and procedures to detect potential hidden failure modes. It is this dedication to long-term reliability that ultimately creates the “ideal product.”

ON Semiconductor achieves ideal IGBT product reliability by formulating a four-step plan to ensure quality and reliability:

1. Strict process control and inspection
2. Thoroughly evaluate design and materials
3. Process average testing, including 100% QA redundant testing
4. Continuous reliability verification through audits and reliability studies

These quality and reliability procedures, coupled with strict incoming inspection and outgoing quality control inspection, ensure product quality from silicon raw material to delivery service.

Reliability test

ON Semiconductor IGBTs undergo an extensive series of reliability tests to verify compliance. These tests are designed to accelerate the failure mechanisms encountered in real-world applications, thereby ensuring satisfactory and reliable performance in "real-world" applications.

The following introduces the reliability tests routinely performed on ON Semiconductor's IGBTs.

High Temperature Reverse Bias (HTRB)

The HTRB test is designed to check the stability of the device with the main blocking junction in "reverse bias" conditions at high temperatures as a function of time.

For a given temperature and voltage applied across the junction, stability over time and leakage current indicate the stability of the junction surface. Therefore, it is a good indicator of device quality and reliability.

For an IGBT, voltage is applied between the collector and emitter, with the gate and emitter shorted. ICES, V(BR)CES, IGES, VGE(th) and VCE(on) are the monitored DC parameters. Failure occurs when leakage current reaches such a high level that power dissipation causes the device to enter thermal runaway. If the device is stable, the leakage current should remain relatively constant and increase only slightly during the test.

Typical conditions:
VCE = 80−100% of maximum rating
VGE = 0 V (short circuit)
TA=150°C or Tjmax
Duration: 1,000 hours to meet certification requirements

High Temperature Gate Bias (HTGB)

The purpose of the HTGB test is to electrically stress the gate oxide at high temperature and at the maximum rated DC bias voltage. This test is designed to detect drift caused by random oxide defects and ionic oxide contamination.

For an IGBT, voltage is applied between the gate and emitter, with the collector and emitter shorted. IGES, VGE(th) and VCE(on) are the monitored DC parameters. Any oxide defects will cause early device failure.

Typical conditions:

VGE=±20V or 100% rated VGE
VCE=0 (short circuit)
TJ=150°C or TJmaximum value
Duration: 1,000 hours to meet certification requirements

High Temperature Storage Life (HTSL) Test

HTSL testing is designed to determine the device's stability, potential to withstand high temperatures, and the package's internal manufacturing integrity. Although the device is not exposed to such extreme temperatures in the field, the purpose of this test is to accelerate any failure mechanisms that may occur at long-term storage temperatures.

Testing is performed by placing the device in a mesh basket and then placing it in a high temperature chamber at controlled ambient temperature as a function of time.

Typical conditions:

TA=150°C (temperature on plastic package)
Duration: 1,000 hours to meet certification requirements

High Humidity and High Temperature Reverse Bias (H3TRB)

H3TRB testing is designed to determine the resistance of components and constituent materials to the combined deterioration effects of long-term operation in high temperature/high humidity environments. This test applies only to unsealed devices.

Humidity has been a traditional factor in semiconductors, especially for plastic packaged devices. Most moisture-related degradation is caused directly or indirectly by moisture penetration through passivating materials and surface corrosion. At ON Semiconductor, this problem has been successfully addressed and controlled through the use of junction "passivation" processes, die coatings, and appropriate selection of packaging materials.

Typical conditions:

VCE=80−100% of maximum rating
VGE=0 (short circuit)
TA=85°C
RH=85%
Duration: 1,000 hours to meet certification requirements

Typical conditions:

VGE≥10V
△TJ=100°C
RθJC=depends on device
Ton,Toff≥30 seconds
Duration: 10,000−15,000 cycles to meet certification requirements

Unbiased High Accelerated Stress Test (UHAST)

UHAST is designed to determine the moisture resistance of a device by subjecting the device to high vapor pressure. This test is only performed on plastic/epoxy packaged devices and not on hermetically sealed packages (i.e. metal can devices). In the test chamber, a tray is placed that holds the device approximately two inches above the surface of the deionized water to prevent condensation from collecting on the device. These test conditions are maintained for at least 24 hours after the appropriate temperature and atmospheric pressure are reached. Then remove the device and air dry. Parameters commonly monitored are leakage current and voltage.

Typical conditions:

TA=131°C
P=14.7 psi
RH=100%
Duration: 72 hours to meet certification requirements

Intermittent operating life (IOL)

The purpose of IOL testing is to determine the chip and /or encapsulates component integrity.

DC power is applied to the device until the desired functional temperature is reached. The power is then turned off and forced air cooling is applied until the junction temperature drops to ambient temperature.

The sequence repeats for the specified number of loops. Care was taken to maintain temperature offsets to ensure reproducible results.
Intermittent operating life testing is used to understand the degree of thermal fatigue of the chip bond interface between the chip and the mounting surface and between the chip and the wire bond interface.

For IGBTs, parameters used to monitor performance include thermal resistance, threshold voltage, on-resistance, gate-emitter leakage current and collector-emitter leakage current.

Failure occurs when thermal fatigue causes the thermal resistance or on-resistance to increase beyond the maximum value specified in the manufacturer's data sheet.

Temperature cycle (TC)

The purpose of temperature cycling testing is to determine the device's resistance to high and low temperature excursions in the air medium and the effects of cycling under these extreme conditions.

The test is performed by alternately placing the devices in separate chambers at high and low temperatures. The air temperature in each chamber is kept uniform through air circulation. The chamber has sufficient thermal capacity to achieve the specified ambient temperature after transferring the device to the chamber.

Each cycle consists of exposure to one extreme temperature for at least 15 minutes, followed by immediate transfer to the other extreme for at least 15 minutes; thus completing a cycle. Note that this is an immediate transfer between temperature extremes and therefore stresses the device more than a non-immediate transfer.

Typical extreme conditions:
−65/+150°C

The number of cycles can be correlated with the severity of the intended application environment. It is generally accepted in the industry that ten cycles are sufficient to determine the quality of a device. Temperature cycling can identify any excess strain that develops between materials inside the device due to differences in expansion coefficients.

Low Temperature Storage Life (LTSL) Test

LTSL testing is designed to determine the device's stability, potential to withstand low temperatures, and the package's internal manufacturing integrity. Although the device is not exposed to such extreme low temperatures in the field, the purpose of this test is to accelerate any failure mechanisms that may occur at long-term storage temperatures.

Typical conditions:

TA=-65°C (temperature on plastic package)
Duration: 1,000 hours to meet certification requirements

Testing is performed by placing the device in a mesh basket and then placing it in a high temperature chamber at controlled ambient temperature as a function of time.

Steady State Operating Life (SSOL) Test

SSOL testing is designed to determine the integrity of chip and/or packaged components under steady-state continuous operating life conditions.

For IGBTs, parameters used to monitor performance include thermal resistance, threshold voltage, on-resistance, gate-emitter leakage current and collector-emitter leakage current.

Typical conditions:

VGE≥10 V
△TJ=100°C
TA=25°C Duration: 1,000 hours to meet certification requirements

Failure occurs when thermal fatigue causes the thermal resistance or on-resistance to increase beyond the maximum value specified in the manufacturer's data sheet.


Figure 1. IGBT wafer manufacturing


Figure 2. Assembly process flow

Environmentally friendly packaging related test items:

A. Physical Dimensions − Perform this test to determine compliance with device outline drawing specifications
B. Visual and Mechanical Inspections − Tests to determine whether a product meets certain appearance and functionality standards (e.g. mark legibility, stains, etc.)
C. Solvent Resistance − Test to determine solderability of device terminals
D. Terminal Strength − This test is a lead bend test used to check lead strength

Every manufacturing process exhibits a distribution of quality and reliability. This distribution must be controlled to ensure a high mean, narrow range, and consistent distribution pattern. This can be achieved through appropriate design and process controls, thereby reducing the need to use screening procedures to eliminate the lower tail portion of the distribution pattern.

Accelerated stress testing

Certain tests in this report far exceed those encountered by the device under normal operating conditions. As a result, the test conditions "accelerate" the failure mechanisms involved and allow ON Semiconductor to predict failure rates in a shorter time than would otherwise be possible. Temperature-dependent failure modes are characterized by the Arrhenius model.

AF=acceleration factor
EA=activation energy (eV)
K=Boltzmann constant (8.62×10E−5eV/K)
T2=working temperature, K
T1=Test temperature, K

Therefore, the equivalent device hours are equal to the acceleration factor (determined by the Arrhenius model) multiplied by the actual device hours.

Data review

High temperature reverse bias (HTRB) is used to determine the stability of the leakage current, which is related to the field distortion of the IGBT. HTRB enhances failure mechanisms through high-temperature reverse-bias testing and is therefore a good indicator of device quality and reliability and can also verify the effectiveness of process controls.

High Temperature Gate Bias (HTGB) is designed to examine the stability of devices over time under "gate bias" forward conditions at accelerated high temperatures. This test is performed to apply electrical stress to the gate oxide to detect drift caused by random oxide defects. This failure mechanism occurs early and randomly in the reliability "bathtub curve" with very low defect rates.

Intermittent Operating Life (IOL) is an excellent accelerated stress test used to determine the performance of a chip and/or packaged component when cycling on (the device heats up due to power dissipation) and cycling off (the device heats up when power is removed) time integrity. This test is probably the most important of all, simulating conditions typically experienced in a "real world" environment. IOL tests die bonds, wire bonds, on devices, off devices, associated device performance and verifies thermal expansion compatibility of all materials. ON Semiconductor performs extensive IOL testing as a continuous process control monitor, which is related to the entire "device system**". ON Semiconductor also performs extensive analysis and comparisons of delta as a function of temperature. ON Semiconductor has determined that in order to effectively stress the device, a ΔTJ of 100°C is necessary, which is well beyond the requirements of many customer applications and dictates the reliability modeling of this device.

Temperature cycling (TC) is also an excellent stress test for determining a device's resistance to high and low temperature excursions in air media. The IOL exerts electrical stress on the "device system" from within, while temperature cycling exerts thermal stress on the "device system" from external environmental conditions.

High Temperature Storage Life (HTSL), High Humidity Temperature Reverse Bias (H3TRB), Thermal Shock (TC), and “pressure cooker” (pressure cooker) are all routine tests, and ON Semiconductor Reliability Engineering considers HTRB, HTGB, IOL, and TC to be The most important test. ON Semiconductor has been in the semiconductor industry for many years and will continue to thrive with continued reliability, quality and customer relationships.


#conduct #reliability #testing #IGBT