Development of a new laser application to enable the effective combination of DBG wafer and DAF for thin die production
DISCO Corporation (Headquarters: Ota-ku, Tokyo, President: Hitoshi Mizorogi) has developed a laser application that only cuts the Die Attach Film (DAF), after the DAF, which is a necessary die bonding material for stacking System in Package (SiP), has been attached to a Dicing Before Grinding (DBG*) processed wafer. This application is effective for thin die production that requires die strength. Processed samples and process methods, based on the application, will be introduced at SEMICON Japan 2005, which will be held from December 7 to 9 (Booth No.: 4, Hall: A1009).
Application Development Background
In recent years, with the growth of SiP being used in mobile devices and the progress of large
diameter wafers, the demand for thinner die has started to increase. Recently, if the wire bonding to the upper stack
die has an overhang, it has been indicated that this could lead to breakage due to the strong bending pressure on the
die. Therefore, greater bending strength improvement of thin die has been requested.
Accordingly, DISCO has developed an application that uses a laser to enable a fusion with the DAF dicing process, which is a necessary die bonding material for stacking SiP, and the DBG process, which is effective in the production of die with high die strength.
Process Summary
The DBG process can improve the bending strength of die due to its ability to significantly lower the backside chipping of the die in the dicing process. However, the wafer can not be applied to the SiP process, which attaches DAF to the wafer backside after wafer thinning. This is because, when the DAF is attached to the backside of a wafer, which has been separated into die by the DBG process, it is necessary to only cut the DAF again. Also, dicing DAF with a conventional blade is not effective due to blade width, processing speed and the ability of the die to stay lined up.
Accordingly, on this occasion, DISCO has developed an application that enables re-dicing of DAF only; using a laser saw that is able to do curvilinear processing.
The process to cut DAF, which has been attached to a DBG processed wafer, is explained in the following two processes.
- Process 1 -
This method cuts the DAF between the die that have been separated with a laser from the front side of a wafer, which has been mounted on dicing frame, like an ordinary full-cut dicing process.
- Process 2 -
After the wafer has been mounted onto a dicing frame, the laser processes the wafer from the backside without removing the front side protection tape. This method only cuts the DAF, allowing the laser to pass through the dicing tape material.
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Process 1 has the merit that additional capital investment is small because it uses a common process; however die shift after DBG is greatly influenced. On the other hand, Process 2 is able to suppress this die shift because both sides of the wafer are held with tape material. However, it might be necessary to change the process because after DAF separation the front side protection tape needs to be peeled off. DISCO is currently optimizing both of these processes and will propose a suitable process to meet the customers' needs.
Also, DISCO has developed special alignment software to support chip shift for the fully automatic dicing saw DFL7160. As a result, the DFL7160 for DAF cutting is able to cut DAF at the high speed of
several 100 mm/sec using curvilinear processing, which is a laser process feature. In addition, DISCO will propose equipment, processes and applications to meet customers' needs, such as options that apply water soluble protection film as a countermeasure to debris.
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Process Introduction Merit
| Photo1: Example of DAF processing with a laser (front side) |
Photo2: Example of DAF processing with a blade (front side) |
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Merits of DBG Process |
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Low risk of damage to a thin wafer |
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Improvement in die strength due to low backside chipping |
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Improvement in the blade dicing process |
| Merits of DAF dicing with a laser for the DBG process |
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Controls DAF burring during blade dicing |
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Realizes high speed DAF cutting |
Future Plan
| 2005/12 |
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Exhibit at SEMICON Japan 2005 from December 7 to 9 |
Test cut requests are accepted at any time to evaluate products and process.
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| * The DBG technology is a reverse of the conventional process "backside grinding → wafer dicing." After first half-cutting the wafer, the die are separated during backside grinding. |
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Contact:
DISCO Corporation
Corporate Strategy Division
Management Strategy Department
Marketing Communications Team
Phone: 81-3-4590-1090Fax: 81-3-4590-1094 |
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