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What's KABRA?
This ingot slicing method forms a flat light-absorbing separation layer (KABRA layer*2) at a specified depth by irradiating a continuous, vertical laser from the upper surface of the SiC ingot, producing wafers.

Conventional laser processing is not suitable for slicing because the modified layer formed by laser irradiation, in principle, extends in the direction of the laser incident (vertical). However, this process succeeds in forming a KABRA layer, which serves as the base point for separation by separating SiC into silicon (Si) and carbon (C) in an amorphous state and making the amorphous carbon efficiently absorb the light*3. In addition, this process can be applied to various types of SiC ingots, including single-crystal (4H, 6H, and semi-insulation) and multi-crystal ingots. This process can be also applied to monocrystal ingots, regardless of the off-angle of the crystal c-axis.
  • *1: Patent pending (53 related patents as of August 4, 2017) / Trademark registered (Registration no. 5850324).
  • *2: Key Amorphous-Black Repetitive Absorption: Forming a layer which becomes the base point for separating the wafer by decomposing SiC into amorphous silicon and amorphous carbon with continuous laser irradiation, and then making the black amorphous efficiently absorb the light.
  • *3: Patent pending.
Process and Flow
1. Form a KABRA layer inside the ingot by laser irradiation.
2. Separate and produce a wafer. Grind the wafer to the specified thickness.
3. Grind the upper surface of the ingot for the next laser irradiation.
Repeat processes 1 to 3 and slice the wafer.

The existing methods for slicing wafers from a SiC ingot mostly used a diamond wire saw. However, these methods require a number of diamond wire saws for mass-producing wafers because the processing time is long due to the high hardness of SiC. The number of wafers produced from a single ingot is also small due to a large amount of material lost in the slicing sections. This has been a major factor in the increased cost of producing SiC power devices.
Advantage

Processing time is
greatly reduced

Existing processes require approx. 3.6 hours to slice a wafer from a Φ6-inch SiC ingot (four to five days for one ingot)*4, 5. In contrast, KABRA can greatly reduce the processing time, requiring only 25 minutes to slice a wafer (approx. 18 hours for one ingot)*6.
  • *4: When producing a specified thickness of 350 µm from Φ6-inch and 20 mm thick SiC ingot.
  • *5: General value based on users' information.
  • *6: Total processing time including laser irradiation, separation, and ingot grinding.


Existing process
existing process
KABRA process
KABRA process

Lapping process is
no longer required

For wire processing, a lapping process is required to remove approx. 50 µm*5 of undulations generated on the surface of a processed wafer. However, KABRA does not require lapping because the wafer undulation after separation can be controlled.
  • *5: General value based on users' information.


Existing process
既存プロセス
KABRA process
KABRAプロセス

Number of wafers produced increases
1.5 times more than
that of existing processes

Although wire processing produces approx. 200 µm*5 of material loss per wafer at the slicing sections (kerf loss), KABRA essentially has no material loss. In addition, the removal amount of the KABRA layer after separation can be suppressed to approx. 100 µm. This improves the number of wafers produced from a single ingot by approx. 1.5 times more than existing processes.
  • *5: General value based on users' information.

Existing process
KABRA process
Existing process*7
KABRA*8
4 inch
6 inch
4 inch
6 inch
Cutting time
2-3 days
4-5 days
8 min.
15 min.
Ingot slice total processing time (per wafer)
1.6-2.4 hr.
3.2-4 hr.
15 min.*9
25 min.*10
Material loss during cutting
(per wafer)
Approx. 200 µm
Approx. 200 µm
None
None
Material loss during grinding
(per wafer)
Approx. 100 µm
(Double-sided lapping)
Approx. 100 µm
(Double-sided lapping)
Approx. 100 µm
(Processing mark grinding)
Approx. 100 µm
(Processing mark grinding)
No. of wafers from one ingot
30 wafers
30 wafers
44 wafers
44 wafers
Lapping
Approx. 7 hr.
Approx. 16 hr.
Not required
Not required
Total processing time per ingot
2-3 days
4-5 days
11 hr.
18 hr.
Comparison table
KABRA process
Existing process
Cutting time
4 inich
6 inch
4 inch
6 inch
2-3 days
4-5 days
8 min.
15 min.
Ingot slice total processing time (per wafer)
4 inich
6 inch
4 inch
6 inch
1.6-2.4 hr.
3.2-4 hr.
15 min.*9
25 min.*10
Material loss during cutting (per wafer)
4 inich
6 inch
4 inch
6 inch
Approx.
200 µm
Approx.
200 µm
None
None
Material loss during grinding (per wafer)
4 inich
6 inch
4 inch
6 inch
Approx.
100 μm
(Double-sided lapping)
Approx.
100 μm
(Double-sided lapping)
Approx.
100 μm
(Processing mark grinding)
Approx.
100 μm
(Processing mark grinding)
No. of wafers from one ingot
4 inich
6 inch
4 inch
6 inch
30 wafers
30 wafers
44 wafers
44 wafers
Lapping
4 inich
6 inch
4 inch
6 inch
Approx.
7 hr.
Approx.
16 hr.
Not
required
Not
required
Total processing time per ingot
4 inich
6 inch
4 inch
6 inch
2-3 days
4-5 days
11 hr.
18 hr.
*4
  • *4: When producing a specified thickness of 350 µm from Φ6-inch and 20 mm thick SiC ingot.
  • *7: When lapping is performed after slicing with a loose abrasive type diamond wire saw (30 multiple wires). All values are general values based on users' information.
  • *8: DISCO’s values are at the time of this releasing.
  • *9: Calculated assuming two minutes for the peeling process and five minutes for the grinding process
  • *10: Calculated assuming two minutes for the peeling process and eight minutes for the grinding process
  • Information updated on September 13, 2017
  • 4 inch: Shorter cutting time and shorter ingot slice total process time
  • 6 inch: Results published

Equipment

DAL7420

DAL7420

Φ6 inch ingot processing

Supports a maximum ingot
thickness of 40 mm

Alignment-free

  • · Automatic ingot thickness measurement function
  • · Detects the orientation flat using auto-alignment
  • Machine dimensions (W×D×H):600×1,045×1,778mm
  • Machine weight:approx. 550 kg
Origin of the name
“Kabra” is also another name for a turnip, and thin slicing is sometimes called “kabra-giri”. There is also a vegetable called “kyo-kabra” which is a traditional food with a long history in Japan. We named this process “KABRA” with Roman letters because slicing a SiC ingot looks like “kabra-giri” and we have the strong desire to contribute to enhancing the world’s convenience by spreading this unique laser slicing technique from Japan throughout the world.
Related Patent
KABRA
Related Patent
Unexamined Patent Publication Nos.
2015-223589/2016-062949/2016-111143/2016-111144/2016-111145/2016-111146/2016-111147/2016-111148/2016-111149/2016-111150/2016-127186/2016-124015/2016-146446/2016-146447/2016-146448/2016-151457/2016-197698/2016-197699/2016-197700/2016-198788/2016-207702/2016-207703/2016-225535/2016-225536/2017-005008/2017-022283/2017-024014/2017-024039/2017-024183/2017-028072/2017-041481/2017-041482/2017-057103/2017-092314/2017-121742/2017-123405
Patent Application Nos.
2016-076734/2016-078613/2016-111163/2016-116126/2016-157879/2016-166476/2016-190952/2016-234958/2016-236701/2017-013073/2017-015742/2017-027113/2017-027114/2017-038435/2017-086074/2017-113391/2017-128507
(As of August 4, 2017)