Stealth Dicing technology is a laser dicing technology that uses lasers, with a completely new concept. The range of devices to which this technology applies will be expanding to include MEMS devices and memory devices and others, due to such features as the "completely dry process", "no kerf loss", "no chipping", "high bending strength" and the like.
SDBG (Stealth Dicing Before Grinding) is a wafer dicing process we offer to improve the structural strength of ultra-thin chip devices less than 50 µm thick. In the SDBG process, a laser beam is first irradiated on a wafer to form modified layers (Stealth Dicing layers or SD layers) and cracks inside the wafer and the wafer is then thinned by grinding and polishing. Since the SD layers are also removed by grinding and polishing, potentially harmful factors that lower the structural strength of chip devices can be eliminated to allow fabricating ultra-thin chips with high quality and high strength.
The SDBG process is also ideal for wafers with DAF (Die Attach Film) as well as Si wafers with stacked patterns including low-k (low dielectric constant) films.
2. Laser irradiation
SD layers are in BHC (*4) state.
3. Grinding and polishing
SD layers are also removed by grinding and polishing.
DAF (*3) is also split during expansion.
(No DAF(*3) processing is needed.)
NOTE: Processes may vary depending on devices.
To make the SDBG process more practical and useful, Stealth Dicing technology utilizes an optical system called LBA (Laser Beam Adjuster) designed specifically for Stealth Dicing using an LCOS-SLM (Liquid Crystal on Silicon - Spatial Light Modulator) that we developed in-house. LCOS-SLM is a reflective type spatial light modulator that can freely modulate the phase of light and display any desired pattern on its liquid crystal surface, allowing high-quality and high-throughput laser processing according to user applications.
The laser beam is expanded to an optimal shape by the beam expander and irradiated onto the LCOS-SLM with any desired pattern displayed. The laser beam is next phase-modulated by the voltage-controlled liquid crystal in LCOS-SLM and passes through the image transfer optical system where an image of the wavefront shape is transferred onto the objective lens surface. The beam then passes through the objective lens and is focused internally within the wafer.
LBA can correct the laser beam focused internally within a wafer or split it into multiple beams for optimal laser dicing. For example, aberration correction improves the beam focusing performance, which extends the cracks stemming from SD layers and so reduces the number of required SD layers. Multipoint simultaneous processing allows forming multiple SD laser beams at the same time along the wafer thickness direction by splitting the laser beam emitted from the objective lens into multiple beams. Each of the split laser beams can be controlled to make aberration corrections and to adjust the laser output ratio according to the dicing depth. When needed, the laser beam can also be split into multiple beams in the laser beam scan direction, making it possible to perform high-speed processing by low frequency laser or to improve the dicing quality during simultaneous processing.
(Red: SD layer / White: Crack)
(Red: SD layer / White: Crack)
NOTE: The laser beam focusing diagram is an image.
Stealth Dicing technology was developed about 20 years ago. Since then its applications have expanded to cover a wide range of devices and materials due to continuous improvements in lasers and optical systems. More recently, mass production of memory devices has started using the SDBG process, which was the goal from the very start of developing Stealth Dicing technology.
When employing our sophisticated Stealth Dicing technology, please be aware that there are also a host of patents for value-added processing that should be checked out in advance. The table below shows patents we currently hold for the SDBG process and related LBA optical systems designed specifically for Stealth Dicing.
(Stealth Dicing Before Grinding)
Stealth Dicing dedicated optical system
LBA (Laser Beam Adjuster)
|Japan||4995256, 4358762, 3762409, 4781661, 4563097||
5863891, 6258787, 5575200, 5255109, 5479925,
5148575, 5692969, 5599563, 4402708, 5775265,
8268704, 7566635, 8304325, 8314013, 8518800,
8518801, 8519511, 8889525, 9142458, 9287177,
9711405, 9553023, 9548246, 9543207, 9543256,
10068801, 10622255, 7939430, 8058103, 8551817
8134099, 9428413, 10622254, 10328521, 8755107,
8526091, 9415461, 9488831, 10324285, 8610993,
|South Korea||10-0715576, 10-0848408, 10-1283294, 10-0827879||
10-1013286, 10-1212936, 10-1302336, 10-1402475,
10-1711247, 10-1564523, 10-1711311, 10-2303178,
10-1839439, 10-1708066, 10-1708161, 10-1605219,
|Taiwan||I278027, I363665, I321828||
I394627, I573649, I595953, I638697, I515065,
60339137.0, 60337873.0, 60313900.0, 60350530.9,
60350449.3, 60352263.7, 602005045636.8,
602008044635.2, 602009051537.3, 602009041607.3,
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