DISCO Technical Review Feb. 2016

Stealth laser dicing engine lineup
Sales Engineering Department
Abstract
Stealth dicing (SD) technology, centered around flash memory (for which ultra-thinning has been
progressing the most) has been rapidly expanding the market for Si materials, such as RFIC for
high-speed wireless communication, MEMS, etc. SD technology can be used not only for Si materials,
but also for sapphire, glass, SiC, GaAs, and GaN. In principle, SD technology requires the laser beam tobe guided into the inner material and focused on a arbitrary position, which means that a laser engine witha long wavelength and a high transmission rate for each material must be used. In this review, we discuss
this topic in detail and present DISCO’s SD engines. DISCO is the official alliance partner of Hamamatsu
Photonics, and we have been given a comprehensive license for the SD technology patent portfolio ofHamamatsu Photonics. We have also been given the patent license for all the SD engines presented in thisreview.
1. Principle of stealth dicing

2. SDE lineupFig. 1 shows the basic principle of stealth dicing(SD) technology[1]. In SD, a laser beam at an
optically transparent wavelength is focused onto
any point within a workpiece. The optical systemused here is adjusted so that the energy density
exceeds the processing threshold value of thetarget material near the focus point. Then, amodified layer (SD layer) is locally formed inside
the workpiece. Because the laser beam is focused
inside the material and the processing starts there,
if the beam is well absorbed inside the material
before reaching the focus point, a sufficient SD
layer cannot be formed.

Each material has a specific transmission
wavelength region. Fig. 2 shows the transmission
wavelength regions of various materials.
The transmission rapidly starts at approximately
1000 nm in single-crystal silicon (Si). However,with the other materials, the laser beam transmits,even at the shorter-wavelength side.
Actual Si semiconductor devices are often used
after impurities are doped by the ion implantation
method or thermal diffusion method. With more
impurities (and therefore lower resistance), thetransmission
regionshiftstothelonger-wavelength side.

Thus, we have developed various SD engines(SDEs) suitable for specific materials. Thisreview presents details and processing results ofeach SDE.

There is a strong correlation between thetransmission region of the material and its
band-gap energy. Table 1 lists the band-gap
energy of each material.
With a smaller the band-gap energy, the beamtransmission range tends to be at theTable 1 Band-gap energy of each materialFig.1 Formation of a modified layer by absorbing
alaser beam inside1Material

Band-gap energy
E(eV)Wavelengthλ(nm)*1SiGaAs
4H-SiCLiNbO3
LiTaO3

1.11
1.43
3.26
3.70
4.60

1,117867
380335270

DISCO Technical Review Feb. 2016

3. Processing examples

longer-wavelength side. Therefore, it is necessary
to select an SDE having a wavelength suitable forthe material to be processed.

Processing examples using materials other than Siand sapphire, which are already well known, will
be described hereinafter. The materials to be
introduced here have attracted attention as
cutting-edge materials for electronic and opticaldevices. Table 3 lists the major device
applications of each material.

Single-crystal Si (thickness: 780 µm) can beprocessed at a high speed with less energy byusing the wavelength band that causes almost noabsorption in Si (1150 nm or more). For thisreason, we have developed SDEs having uniquelong-wavelength bands (SDE03 and SDE06 in
Table 2). Table 2 lists SDEs that DISCO hasdeveloped and made available.

With blade dicing, these hard and brittle materials
must be processed at a slow speed in order tominimize chipping. It is expected that high speedwith high quality can be achieved by replacing
blade dicing with the SD processing.

Table 2 DISCO SDE lineup
Material

SDE
SDE01/SDE05
SDE03/SDE06

Si
Sapphire

Wavelength
Near infraredlight
Near infraredlight

SDE31/SDE34

LiTaO3
LiNbO3GaN
Sapphire
Glass
SiC
GaAs
InP

SDE33

Visible light

SDE12
SDE41

Visible light
Visible light
Near infrared
light

SDE21

Fig. 3 shows photographs of each material
processed with the SDEs in Table 2, and theirprocessing parameters.

100

Single crystal Si(780um)

90

Sapphire(150um)

80

Glass(1008um)

Transmission rate (%)

70
LT(357um)

60
50

LN(360um)

40
4H-SiC(366um)

3020GaAs(300um)

101500

1400

1300

1200

1100

1000

900

800

700

600

500

400

3000

Wavelength (nm)Fig.2 Beam transmission spectrum of each material
Measurement instrument: Spectrophotometer
Manufactured by JASCO Corporation
Model no.V-670

Both sides of all materials used are mirror-finished surfaces.
Transmission rates include losses due to optical reflection on
the front and back surfaces of the materials.
Measured by DISCO using the measurement instrument shownat the left side.

2DISCO Technical Review Feb. 2016

Semiconductor and LED manufacturers who useSDEs not licensed by Hamamatsu Photonics andtheir products probably infringe these SD patents.

Table 3 Major device applications of eachmaterials
MaterialGaAs

SiC

LiTaO3
LiNbO3
GlassGaNInP

We have been granted a comprehensive license
for the SD technology from Hamamatsu
Photonics and supply our equipment to device
manufacturers. By doing so, our users canmanufacture and sell devices without infringing
the rights of Hamamatsu Photonics (Fig. 4).

Major device applications
Hetero-bipolar transistors (HBTs)
High-density backplane-mounted(HBMT) connectors
Red and infrared ligt emitting diodes(LEDs)
Semiconductor lasers
Power semiconductor devices
Shot key barrier diodes
Metal-oxide-semiconductor field-effectransistors (MOSFETs)
Insulated-gate bipolar transistors(IGBTs)
Blue light-emitting diodes (LEDs)

Hamamatasu Photonics K.K.
SDE is soldDISCO Corporation
Patent license is
automatically granted bybuying equipment fromDISCO
Semiconductor manufacturers

Surface acoustic wave (SAW) devices
Optical filters
Substrates for high-frequency devices
Medical applications
High-frequency devices
Power semiconductors
Blue light-emitting diodes (LEDs)
High-electron-mobility transistors(HEMTs)
Hetero-bipolar transistors (HBTs)
Semiconductor lasers

LED manufacturers

Fig.4 Patent licensing structure of the SD

5. Conclusion
SD is an innovative technology to realize further
thinning of Si devices and to process materials
that are difficult to process with conventional
blade dicing at high speed with high quality. It isalso an environmentally-friendly process that does
not require deionized water, and it reduces
wastewater treatment because it is a completely
dry process that does not require cleaning
operations during dicing.

4. Intellectual property rights of stealth dicing
Hamamatsu Photonics K.K. owns most of thepatents relevant to the basic principle andprocesses of SD technology. A list of their patents
can be reviewed on their official website athttps://www.hamamatsu.com/jp/en/technology/innovation/sd/index.html.

Fig.3 Microscope images and processing parameters of each material

3

DISCO Technical Review Feb. 2016

This technology has been applied mainly in thefield of Si materials, such as radio frequency
integratedcircuits(RFICs)
andmicroelectromechanical systems (MEMS) for
wireless communication, in addition to flash
memories, and in the field of sapphire materials
for LEDs. These markets are rapidly expanding.
Both fields are now entering into the phase where
further enhancement of productivity and lower
costs are strongly demanded. In order to meetthese demands, we are now accelerating thedevelopment of SDE.
We have also emphasized technical development
for materials other than Si. We strive to ensurethat our innovation will lead to higher
productivity and quality than those of the existing
technology, and accelerate the introduction of ournew engines to the market. We have already soldour SDEs for new materials, such as glasses,lithium tantalate (LiTaO3), and lithium niobate(LiNbO3). The scope of applications will expand
to cover even more types of materials.

References[1] D. Kawaguchi, Hamamatsu Photonics K.K.,"Application of the internal resorption typelaser dicing technology for chemicallytempered glass," NEW GLASS, Vol. 27, No.
106 (2012).

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