Many friends who are engaged in semiconductor research and development, chip packaging and testing, and material analysis will encounter a difficult problem: if you want to see the internal defects at the bottom of the chip and under the silicon substrate, most traditional testing methods require grinding, slicing, and opening, which is destructive testing. Once the dissection is completed, the sample cannot be reused, which not only consumes a lot of time, but also directly scraps expensive chip samples, which greatly increases the cost of R&D testing. At this time, short-wave infrared JM-SWIR (900-1700nm band) non-destructive microscopy technology has become the preferred solution for more and more laboratories.
Ordinary visible light cannot penetrate the silicon material, so the naked eye and conventional optical microscopy can only see the surface of the chip. And 900-1700nm short-wave infrared light can penetrate the silicon substrate. With an infrared optical system and an InGaAs imaging camera, the imaging is done directly from the back of the chip without opening the lid or slicing, leaving the sample intact for true nondestructive testing.
Tip: This technology has boundaries, not all materials can penetrate, and the type of substrate directly determines the imaging effect. Consult an instrumentation professional before selecting equipment.
Second, short-wave infrared microscopy, which samples are suitable?
VCSEL photoelectric chips are commonly used in the fields of optical communication and 3D sensing. They can screen for chip cavity damage, substrate microcracks, weld layer holes, and abnormal bonding sites, which are widely used in today's scenarios.
Faraday materials (rare earth-based magneto-optical crystals such as TGG, TSAG, CeF, gallium garnet, etc.) mostly have good permeability at short-wave infrared 9001700nm. Short-wave infrared microscopy can be used for transmission observation, but there are boundary conditions, not unconditional full penetration.
The silicon wafer and silicon-based bare wafer manufacturing process detects sub-surface defects caused by silicon wafer creepage, internal scratches, substrate impurities, and grinding.
The memory chip, power device, MOS, IGBT, and various SOC package samples of the silicon-based semiconductor package device are observed for internal voids, wire offsets, and cracks at the bottom of the chip.
Flip-chip and advanced packaging samples do not need to remove the packaging shell, penetrate the silicon substrate, and observe the bottom bumps, solder joint defects, and interface abnormalities.
In the research and development of silicon-based MEMS sensors, silicon thin film materials in university laboratories, and new materials, internal observation and failure mechanism analysis of various silicon-based microstructure devices.
Thick metal completely blocks the optical path, thick silicon carbide substrates, thick gallium arsenide and other non-silicon substrates, full ceramic substrate samples, short-wave infrared is difficult to penetrate, and this scheme is not recommended.
With the help of short-wave infrared microscopy equipment, a variety of hidden defects inside silicon-based devices can be effectively identified: substrate micro-cracks, wafer fragmentation, encapsulated solder voids, bond offsets, internal contaminants, underlying circuit abnormalities, dielectric layer damage, and other sub-surface problems.
Many practitioners are prone to pitfalls in their initial selection. Here are some practical experiences in the industry:
1. The objective lens cannot be mixed: ordinary visible light lenses cannot meet the needs of short-wave infrared imaging, and the chromatic aberration is serious. Be sure to choose an infinity infrared objective lens for SWIR that has been corrected in the 900-1700nm band;
2. Imaging cameras: InGaAs sensor cameras are preferred, with high sensitivity for short-wave infrared bands;
3. Lighting system: Support multi-band infrared light source switching (1200/1300/1400/1550nm), adjust the wavelength for different samples to improve defect contrast;
4. Optical path architecture: coaxial falling Kohler illumination structure, more suitable for the back of the chip observation scene. The JM-SWIR series of short-wave infrared microscopes are built for semiconductor packaging and testing, university laboratories, equipped with infrared special optical paths, and coaxial Kohler incident illumination. They are widely used in VCSEL, wafer, and chip failure non-destructive analysis.
Tell us the material, the feature you need to see and the magnification range. We will recommend a configuration and quote it.
