Introducing the Fully Automatic Thinning Process of Sapphire Substrates for LED
DISCO Corporation (Head Office: Ota-ku, Tokyo; President: Kazuma Sekiya) has developed the fully automatic thinning (grinding and polishing) process of sapphire substrates for LED using DISCO fully automatic grinder/polisher DGP8761. This innovation greatly reduces the processing steps required for LED manufacturing as well as the environmental impact.
Development Background
Sapphire, which is used as the LED substrate, is very difficult to process. Because of this, in the existing thinning process, different machines are used in each step of grinding, lapping, polishing, and cleaning, and therefore a fully automatic thinning system has been strongly demanded. Furthermore, manual labor is required between these steps and machines, such as handling of workpieces, so a reduction in the running cost is also a challenge.
Now, DISCO has developed the process in which one machine can complete the sapphire substrate thinning (grinding and polishing) fully automatically.
Advantages of the Fully Automatic Thinning Process
|
<Less processing steps>
|
| Conventionally the sapphire substrate is thinned following the steps shown in Fig. 1 using different machines in each step. Meanwhile, the process developed by DISCO realizes the fully automatic thinning from grinding to polishing after the wafer mounter has mounted a sapphire substrate onto the dicing frame (Fig. 2).
|
|
Fig. 1: Existing Sapphire Substrate Thinning Process (Example)
|
|
1) |
Securing the sapphire substrate on the alumina ceramic substrate with wax |
|
2) |
Rough grinding using a diamond wheel |
|
3) |
Lapping using diamond slurry |
|
4) |
Polishing |
|
5) |
Separating from the alumina ceramic substrate by heating |
|
6) |
Cleaning |
|
7)
|
Remounting onto the dicing frame
|
|
→ Dicing process using a laser saw
|
|
|
|
|
|
Fig 2: Sapphire Substrate Thinning Process Developed by DISCO
|
|
1)
|
Mounting the sapphire substrate onto the dicing frame
|
|
2)
|
Fully automatic grinding and polishing using the DGP8761
|
|
→ Dicing process using a laser saw
|
|
|
|
|
|
The conventional thinning process consists of seven steps, whereas the DISCO developed process has only two steps while maintaining an equal processing quality.
Since the new process mounts the sapphire substrate onto the dicing frame in the thinning process, the conventional steps of securing, separating, and remounting are not required. Accordingly, the sapphire substrate can be sent to the dicing (singulation) process without doing any extra work.
|
|
<Fully automatic process eliminating risks of damage between steps>
|
|
Since the conventional thinning process uses an independent machine at each step, the process has various problems, including a fear of damaging the ultrathin sapphire substrate during separation, cleaning, or remounting on the tape frame.
The process developed by DISCO fully automatically thins the substrate using only one machine, so that it significantly reduces the risk of damaging the substrate in the process.
|
|
|
<Process causing less environmental impact>
|
|
The new process secures the sapphire substrate using dicing tape. This eliminates the hot-melted wax that is used in the conventional process to secure the substrate. In addition, dry polishing, which is DISCO's exclusive technology, is adopted in the polishing step, so the conventionally required chemicals such as slurries for lapping and polishing, which have large environmental impact, are not required. The cleaning uses only deionized water. In the end, DISCO realizes the process with minimized environmental impact.
|
 |
 |
Fully Automatic Grinder/Polisher
DGP8761 |
Configuration of the Grinding
and Polishing Section |
Dicing after Thinning
For the dicing process after thinning, DISCO recommends our stealth dicing (SD) jointly developed with Hamamatsu Photonics or ablation processing.
The SD focuses laser energy on the inside of the sapphire substrate and separates by breaking using the modified layer formed there as a starting point. This technology does not produce much thermal impact on the epilayer, so that it does not reduce the brightness. Therefore, SD has been adopted mainly as the means of mass-producing high-brightness LED for high-end products.
The ablation processing focuses laser energy on a minute area and sublimes or evaporates the solid. This processing method grooves the substrate and conducts breaking or singulation starting from the groove. Compared with the SD, the ablation may slightly reduce brightness, but it has an advantage in initial cost and therefore it has been adopted in the manufacturing of medium to high-brightness LED.
Reference:Processing Sapphires with Lasers
Schedule
|
Unveiling at SEMICON Japan
|
: |
December 2009
|
|
Test cuts
|
: |
Accepting requests
|
|
|
|
