Electrical Test and QML Test
FUNCTIONAL ELECTRICAL TESTING
The functional test group performs tests several times during the manufacturing process to ensure product integrity and QML quality compliance. The functional test program development begins with the electrical reverse engineering using a sample part. The measured data is compared to the procurement specification. Characteristics which are critical to the correct operation or design of the microcircuit but are not specified in the original documentation are also measured. The collected data is used by the design team to create the emulated microcircuit.
ELECTRICAL TESTING TO VALIDATE WAFER FABRICATION
Wafer level testing and reliability screening are performed in compliance with MIL-PRF-38535 procedures to determine product suitability for assembly and packaging of the die. Wafer Acceptance Testing (WAT), also known as Process Control Monitoring or the Parametric Monitor, is performed to measure the characteristics of the devices and determine uniformity across a wafer. WAT verifies wafer processing has been executed properly and validates that the transistor characteristics are within the accepted range for a given process. The parametric measurements taken include threshold voltage, sheet resistance, contact resistance, transistor gain, and breakdown voltage. Between 100 to 500 parameters are measured from each test site.
Wafer Level Reliability (WLR) testing is performed on the Technology Characterization Vehicle (TCV), which is a structure to obtain measurements that provide the lifetime expectations of the products based on susceptibility to intrinsic failure or wear-out mechanisms. This ensures that all wafer processing produces acceptable levels of reliability. Measurements are taken to analyze structures for metal electromigration, hot carrier degradation, oxide integrity, and other indicators performance over time.
WAT and WLR tests are performed in a climate controlled micro-chamber providing the added capability to perform parametric testing over the full mil-spec temperature range (-55 °C to +125 °C).
WAFER SORT (FUNCTIONAL) ELECTRICAL TESTING
After the wafer manufacturing process in has been completed, wafer sort testing is performed to verify functional performance of the microcircuit. Following assembly of production devices into packages, each microcircuit is tested over the full operating range to ensure that it is fully compliant to the required specification.
Automated Test Equipment (ATE) systems are used to perform both digital and analog testing. The ATE systems use of customized test programs and dedicated test fixture hardware.
MIL-PRF-38535 QML QUALIFICATION TESTING
SRI maintains capabilities to perform MIL-PRF-38535 qualification and screening tests with DLA issued lab suitability in conformance to the requirements for military grade microcircuits (MIL-STD-883 Test Methods).
With on-site mechanical, environmental and package test screening equipment we routinely perform test methods shown in the inset Table. These tests are performed to ensure full conformance to MIL-PRF-38535 and MIL-STD-883. All devices are fully screened, including Wafer lot acceptance, visual inspection, temp cycling, constant acceleration, fine leak, gross leak, pre-burn-in and post burn-in electrical tests. Additional test methods are performed as per MIL-PRF-35835 to verify suitability of the microcircuit.