In the wafer dicing process, due to special requirements, high pressure cleaning is performed on the die after dicing to remove surface contaminants. This step is critical for ensuring the quality of subsequent wafer grinding and polishing processes.
1. Definition of High Pressure Cleaning
High pressure cleaning refers to a process that, after wafer dicing, uses high-pressure (typically tens to hundreds of bar), high-speed flowing DI Water (Deionized Water), or is combined with a dedicated cleaning solution to precisely clean residual contaminants on the wafer surface and inside the dicing grooves. It serves as a key pre-treatment step for post-dicing precision grinding or Chemical Mechanical Polishing (CMP).
2. Core Principles
The essence of high pressure cleaning lies in the synergistic effect of “kinetic energy stripping + chemical decomposition”:
Physical Scouring: High-pressure water flow (similar to a high-pressure water gun removing stains) generates strong impact force, directly stripping dicing debris (such as silicon powder) and dicing fluid residues adhering to the wafer surface. This prevents debris from scratching the wafer during subsequent abrasive processing.
Chemical Cleaning: Surfactants in the cleaning solution decompose oil stains and organic residues, reducing the adhesion between contaminants and the wafer surface. This makes it easier for the water flow to wash away contaminants, ensuring a clean surface for subsequent processes like wafer bonding or thin-film deposition.
3. Why high-pressure cleaning is necessary (reasons)
Without cleaning after dicing, residual contaminants will directly cause subsequent process failures. The core reasons include:
Impact on Bonding/Packaging: Residual silicon powder and dicing fluid will lead to poor bonding between the chip and the substrate, resulting in poor circuit contact. This issue is irreversible and can render the chip useless even if subsequent grinding or polishing is performed.
Device Damage: Tiny silicon debris may scratch the circuit layer on the wafer surface or “sinter” onto the chip during subsequent high-temperature processes, causing device short circuits. These scratches are difficult to repair through post-processing like polishing pad grinding.
Impact on Inspection Accuracy: Contaminants can cover micro-defects (such as cracks and scratches) on the wafer surface, leading to misjudgment by inspection equipment. This allows defective products to flow into the next process (e.g., wafer thinning), increasing production costs and reducing overall yield.