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A diffusion furnace is a specialized piece of equipment used to introduce impurities into semiconductor wafers in a controlled manner. These impurities, called dopants, change the electrical properties of semiconductors, allowing different types of electronic components to be made. This controlled diffusion process is critical to the production of transistors, diodes and integrated circuits.

Currently, many semiconductor devices employ mesa device structures, which are predominantly created through two types of etching: wet etching and dry etching. While the simple and rapid wet etching plays a significant role in semiconductor device fabrication, it has inherent drawbacks such as isotropic etching and poor uniformity, which result in limited control when transferring small-sized patterns. Dry etching, however, with its high anisotropy, good uniformity, and repeatability, has become prominent in semiconductor device fabrication processes. The term “dry etching” broadly refers to any non-wet etching technology used for removing surface materials and transferring micro and nano patterns, including laser etching, plasma etching, and chemical vapor etching. The dry etching discussed in this text specifically pertains to the narrow application of processes using plasma discharge—either physical or chemical—to modify material surfaces.

Defect-free epitaxial growth occurs when one crystal lattice has nearly identical lattice constants to another. Growth happens when lattice sites of the two lattices at the interface region are approximately matched, which is possible with a small lattice mismatch (less than 0.1%). This approximate matching is achieved even with elastic strain at the interface, where each atom is slightly displaced from its original position in the boundary layer. While a small amount of strain is tolerable for thin layers and even desirable for quantum well lasers, the strain energy stored in the crystal is generally lowered by the formation of misfit dislocations, which involve a missing row of atoms in one lattice.

Both epitaxial and diffused wafers are essential materials in semiconductor manufacturing, but they differ significantly in their fabrication processes and target applications. This article delves into the key distinctions between these wafer types.

The three primary methods used in monocrystalline silicon manufacturing are the Czochralski (CZ) method, the Kyropoulos method, and the Float Zone (FZ) method.