Wet Polishing (CMP etc.)

Solutions

With the reduction in height and size of IC packages, there is increased demand for thinner built-in die in silicon devices. Therefore, the stress relief process is carried out to improve die strength after wafer backgrinding. Furthermore, a polishing process is also required after backgrinding to improve performance for devices such as high luminance sapphire (Al₂O₃) substrate for LEDs, lithium tantalate (LiTaO₃) / lithium niobate (LiNbO₃) substrate for high-speed communication device SAW filters, and silicon carbide (SiC) substrate for power devices.
Typical CMP equipment places the wafer above and the polishing pad below. In contrast, DISCO equipment possess a feed axis and places the polishing pad above and the wafer below. This structure is called “in-feed polishing” and is used for both dry polishing and wet polishing (polishing technique using chemicals, among which the most well-known process is CMP). DISCO’s wet polishing, introduced here, realizes scratch reduction, mirror surface finish, and improvements to cleanliness. Furthermore, depending on the material, an Epi Ready* finish can be achieved.

*Epi Ready: surfaces and materials that enable epitaxial growth.

Characteristics of Wet Polishing Process

Low-load, high-rotation polishing

Figure 2. Processing image of wet polishing

Main Effects of Wet Polishing Process

Mirror surface finish processing
High cleanliness
Depending on the material, low number of scratches and Epi Ready finish can be achieved

Application Examples

Polishing for wafer production (substrate manufacturing process)
- Silicon carbide (SiC)
- Sapphire (Al₂O₃)
- Lithium tantalite (LiTaO₃) / Lithium niobate (LiNbO₃)
Stress relief after backgrinding
- Silicon (Si)
- Sapphire (Al₂O₃)
- Lithium tantalate (LiTaO₃) / Lithium tantalate (LiTaO₃) on on silicon (Si)
- Gallium arsenide (GaAs)
- Indium phosphide (InP)
Polishing before Cu-Cu bonding
Regeneration processing of silicon (Si) wafers

Figure 3. Polishing rate with wet polishing

Compatible Equipment

Our product line-up provides highly extensible capabilities that can be used to match our customer’s operating environment and can also be used for a wide range of applications.