Thermal Imaging Microscope for Semiconductor Device Failure Analysis
Sentris can perform the same temperature analysis and detect identical types of semiconductor device defects as competing thermal emission systems.
- Leakage current
- Resistive shorts
- Oxide layer breakdown
- Device temperature mapping
- Thermal resistance evaluation
The primary difference between Sentris and competing Lock-in Thermography systems for semiconductor failure analysis is the infrared camera technology used. Sentris includes an uncooled LWIR (7-14 microns) microbolometer camera with <40mK NETD* and 60Hz image capture rate. Competing systems utilizes cooled MWIR (3-5 microns) cameras with ~20mK NETD* and ~100Hz image capture rate.
* Noise Equivalent Temperature Difference (NETD) specifies the smallest temperature difference that can be detected.
Lock-in thermography (LIT) test sensitivity is primarily dependent on NETD and the number of images captured during a test. LIT Sensitivity (theoretical) = 0.5 * NETD / (square root(# test images captured)). Therefore, for a specific test time length, tests can be more than twice as sensitive using cooled cameras. Sentris test sensitivity can be increased however, by simply extending the test time.
When lenses are properly designed, spatial resolution is limited by diffraction to approximately ½ the working wavelength. The working wavelength of the Sentris LWIR camera is approximately 10 microns, and therefore the minimum possible spatial resolution is 5 microns. The working wavelength of cooled MWIR cameras is approximately 4 microns, and therefore the minimum possible spatial resolution is 2 microns. It should be noted however, that in practice, an increase in lens magnification will generally lead to a reduction in lens numerical aperture (and working distance), and an increase in diffraction, limiting the effective spatial resolution to <2 microns.
The cameras in competing systems include detector assemblies that are typically cooled by mechanical Stirling engines. Stirling engines are expensive, complex devices whose reliability should be considered when purchasing a system intended for many years of use.
The Sentris Lock-in Thermography software-driven process was developed by Optotherm to simplify and reduce the cost of semiconductor failure analysis. Competing lock-in thermography systems include complex and expensive lock-in amplifiers in order to synchronize captured thermal images with device power.
By eliminating the expense involved with cooled infrared cameras and lock-in hardware, Sentris can be offered for approximately 1/3 the cost of competing systems.