Wafer reclaiming process refers to the recycling of silicon wafers. A reclaimed wafer is one that has been treated, stripped, polished and cleaned. It is then used again in manufacturing or testing of various devices. Usually, the secondhand wafer has multiple layers of different materials which make it useless to qualify the standards defined by the manufacturing, testing or research industries. The reclaim industry processes these wafers to make them useful and cost-effective.
Quality Silicon Wafers are thinner than virgin wafers but are equally useful for testing and less complex functions. The reclaim process includes a few necessary steps which are mentioned below
The very first step is of sorting which is critical and helps to prevent the reclaim line from being contaminated with different metallic contents present on a used silicon wafer. Sorting includes a keen inspection of wafers. The process starts with visual inspection followed with wafer type determination. The silicon wafers also pass through measurement of dopant and a few mechanical parameters.
The stripping step may vary as per the current condition and previous processing type of the used wafer. The process is conducted in an automated wet immersion batch tanks with solutions like SPM, alkaline etchs like KOH, Nitric acid, Phosphoric acid or concentrated HF etch. These chemicals are added depending upon the types of metal residues present. Quality Silicon Wafers from reclaim industry usually pass through additional pre-treatment.
3: Lapping and Grinding
Grinding is the process of removing SOI films from the silicon wafer to improve the quality and functionality. Grinding is similar to the process of CMP, but it is much faster. After the grinding process, the wafer requires smoothing and polishing to create uniformity.
After grinding the wafer is set for a mechanical process called lapping. A pad with polishing liquid is rubbed against the wafer to get rid of excess silicon from a wafer substrate. It gives semi-reflective and a dull grey finish. The edges of the wafer are rounded to create a finished look.
There are two varieties of polishes- single side polishing and double side polishing. The process is a blend of chemical and mechanical polishing. Double-sided polishing produces the lowest TTV. After polishing the reclaimed wafer becomes thinner than the virgin wafer. If required, metallic contaminants and unwanted particles are removed after the polishing.
Batch immersion tanks are required to perform a final cleaning step. At this stage, RCA critical cleaning process is performed which include a combination of H2O: NH4OH: H2O2 at stage one, H2O:HCl: H2O2 at step 2. Reduction of metal levels. After the completion of the cleaning process, a surface tension dryer is used.
It is the final step where the wafer is sorted again by the thickness and other defect levels before sending back to the market. Troubleshooting equipment is used to perform the inspection.
Our expertise in Silicon goes back to 1990. Our process engineers have been at the forefront of Silicon wafer production in virtually every step of the process, including such areas as Silicon crystal growth, slicing, lapping, stepped-polishing, single side polish, double-side polish, edge grind/shape, etching, cleaning, QA-inspections, process engineering and development, polishing plant design/production, special tool manufacturing, training, and packaging. We are highly skilled in all diameters of Silicon wafers from 50mm to 300mm.
Thin Film Oxide
Silicon On Insulator (SOI)
Ultra Flat Wafers < 1um
Our substrates include single Element Semiconductors, Insulator, Graded Semiconductors, Ternary Semiconductors, Superconducting Glass, and more.
Our wafer sizes: 2”, 4” and 6”; Diced 4”/100mm wafer in 5x5mm Si chips; Ultra-flat 5x5mm Si chips; Ultra-flat 5x5mm Si chips with 200nm thermal SiO2; Silicon Finder Grid ultra-flat Si substrate.
Silicon standard wafer sizes are available in a variety of diameters from 25.4 mm (1 inch) to 300 mm (11.8 inches).
Our services include: precision waterjet cutting & shaping; patterned wafer cutting & dicing; edge trimming; hole cutting; prototyping; wafer grinding, dicing inspection and packaging.