Application of Boron Carbide in Wafer Polishing

Advantages of Boron Carbide (B₄C) for Semiconductor Wafer Polishing

1. Its hardness falls between silicon carbide and diamond, delivering moderate cutting capacity with fewer deep scratches and edge chipping defects.
2. Chemically inert, it will not react with wafer substrates during polishing, effectively reducing surface contamination.
3. It can be processed into submicron and nano-scale ultrafine powder to meet the requirements of ultra-precision mirror polishing of wafers.
4. Excellent thermal stability; no softening or agglomeration occurs under heat generated during lapping and polishing.

Applicable Wafer Types

1. Silicon Carbide (SiC) Wafers

   As the core substrate for third-generation semiconductors, boron carbide serves as one of the mainstream abrasives for rough and fine lapping of SiC wafers. It ensures stable material removal rate at a far lower cost than diamond powder.

2. Sapphire (Al₂O₃) Wafers

   Base material for LED epitaxial wafers, used for thinning, double-sided lapping, edge chamfering and pre-polishing after slicing.

3. Aluminum Nitride, Gallium Nitride and Alumina Ceramic Wafers

   Applied for rough and intermediate polishing of power device substrates and heat dissipation substrates.

4. Quartz Wafers & Silicon Wafers (Pre-rough Lapping Treatment)

   Used for slicing and thinning rough polishing of silicon wafers; partially replaces green silicon carbide to improve lapping efficiency.

Specific Processing Applications

1. Post-slicing Wafer Rough Lapping

   Eliminate wire saw lines, surface irregularities and subsurface damage layers, and rapidly level wafer thickness by adopting micron-sized boron carbide powder.

2. Double-sided Fine Lapping

   Control TTV (Total Thickness Variation) and warp value, improve wafer parallelism, and serve as pre-treatment before CMP chemical mechanical polishing.

3. Wafer Edge Chamfer Lapping

   Prevent cracking and edge chipping in subsequent processes; boron carbide slurry is applied for wet chamfering on edge grinding machines.

4. Intermediate Pre-polishing

   Positioned between rough lapping and final CMP polishing, it reduces surface roughness rapidly and cuts consumption of subsequent polishing consumables.

5. Surface Dressing for Ceramic Carriers and Suction Chucks

   Dress the flatness of lapping plates and ceramic backing plates, so as to guarantee flatness precision in wafer processing.

Grade Requirements for Semiconductor-Grade Boron Carbide

1. High purity: Extremely low content of free carbon and metallic impurities (Fe, Al, Ca, Mg) to avoid metal ion contamination on wafers.
2. Narrow particle size distribution: Free of oversized particles to prevent scratches on wafer surfaces.
3. Controllable particle shaping/spheroidization: Powder can be shape-modified on demand to balance material removal rate and surface roughness.
4. Excellent dispersibility: Resists sedimentation and agglomeration when formulated into water-based polishing slurry.

Comparative Advantages vs. Diamond & Silicon Carbide

1. Compared with diamond powder: Remarkable cost advantage for mass rough and intermediate lapping, avoiding deep subsurface damage caused by excessive cutting of diamond abrasives.
2. Compared with green silicon carbide: Higher hardness and faster material removal rate, showing outstanding performance on ultra-hard substrates such as silicon carbide and sapphire.