Wafer production process
Broadly speaking, wafer production consists of two main stages, ingot manufacturing and wafer manufacturing, which divide into the following main steps (ingot manufacturing covers only the first step; all others belong to wafer manufacturing, which is why they are sometimes collectively called post-slicing processing):
Ingot growth -- ingot cropping and inspection -- outer diameter grinding -- slicing -- edge rounding -- surface lapping -- etching -- defect removal -- polishing -- cleaning -- inspection -- packaging
1. Ingot growth: this step can be further divided into:
1) Melt Down: chunks of high-purity polysilicon are placed in a quartz crucible and heated above their melting point of 1420°C until completely melted.
2) Neck Growth: once the temperature of the silicon melt is stable, a seed crystal with <1.0.0> orientation is slowly lowered into it and then slowly pulled up, reducing the diameter to a certain size (typically about 6mm). This diameter is held while pulling 100-200mm to eliminate orientation differences in the grain arrangement of the seed.
3) Crown Growth: after neck growth, the pulling speed and temperature are gradually lowered so that the diameter widens to the required size (e.g. 5, 6, 8 or 12 inches).
4) Body Growth: the pulling speed and melt temperature are continuously adjusted to keep the ingot diameter constant until the ingot reaches the specified length.
5) Tail Growth: once the ingot reaches the specified length, the pulling speed and melt temperature are gradually increased so that the diameter tapers, avoiding dislocations and slip caused by thermal stress, until the ingot separates completely from the melt surface. This yields a complete ingot.
2 and Cutting & Inspection
3. Surface Grinding & Shaping: during growth the outer diameter and roundness deviate somewhat and the cylindrical surface is uneven, so the outer diameter must be trimmed and ground until size and shape errors are within the allowed tolerance.
4. Wire Saw Slicing: because silicon is very hard, this step uses a thin ring-shaped saw blade with diamond particles set into its inner edge to cut the ingot into thin wafers.
5 Edge Profiling dedicated automatic
6. Lapping: lapping removes saw marks and damage left on the wafer surface by slicing, bringing the surface to the required finish.
7. Etching: chemical etching removes the damaged layer created on the wafer surface by processing stress in the previous steps.
8. Gettering: sandblasting is used to move flaws and defects on the wafer into the lower layer, to facilitate later processing. 9. Polishing: the edge and surface of the wafer are polished, first to further remove particles adhering to the wafer, and second to obtain excellent surface flatness for the wafer processing steps described later.
10. Cleaning: the finished wafers receive a final thorough cleaning and air drying.
11. Inspection: a final full inspection ensures that the product meets the specified size, shape, surface finish, flatness and other technical requirements.
12. Packing: finished wafers are separated, wrapped and boxed with flexible materials, ready to be sent on to the chip manufacturing workshop or shipped to the ordering customer.
