July 12th, 2019
Development of modern integrated circuits (ICs), advanced power electronics for EV and HEV, and photovoltaics requires a cross-section of industrial processing techniques, spanning from initial crystal growth to thin-film deposition and photolithography. First, a defect-free single crystalline boule is generated in a specialized furnace and dopants are added to alter the material’s semiconducting behavior. Next, a thin wafer must be extracted from the ingot using abrasive wire sawing.
Wire sawing is among the current most desirable tools for electronic substrate slicing, due to its outstanding precision and ability to extract wafers with comparatively uniform topographical properties. There are numerous forms of wire sawing available in construction, parts manufacturing, and research engineering applications; but there are two clear frontrunners for electronic substrate slicing:
• Loose abrasive wire sawing
• Fixed diamond wire sawing
In this blog post, Saint-Gobain Surface Conditioning will outline each of these processes in a little more depth.
Loose abrasive wire sawing is an established tool used to wafer single-crystal ingots with varying chemistries including aluminum nitride (AlN), gallium nitride (GaN), sapphire (Al2O3), silicon (Si), and silicon carbide (SiC). The kerf of conventional bladed cutting technologies alongside the relatively poor planarity of the surface and insufficient hardness makes purely mechanical saws (bandsaws, dicing blades) and other cutting tools unsuitable for electronic substrate slicing. Chemical enhancements to the wiresaw vehicle are important to optimize process cost and recycleability.
When optimized, loose abrasive wire sawing offers remarkably improved precision for wafer extraction by eschewing saw teeth in favor of a composite of products: a continuous length of wire or cable with a loose powder or slurry abrasive. These products work in tandem to machine the edge of an ingot with minimal chipping. The rapid motion of the wire abrades the abrasive particles against the semiconductor until a planar surface has been sliced clean across the ingot. This process is repeated below the initial cut to extract a uniform wafer of microscale thickness.
High throughput loose abrasive wire sawing demands extremely-hard, chemically-stable abrasive particles to ensure the production of uniform and homogenous wafers with outstanding degrees of planarity. This explains why diamond is the most commercially-available material for both loose and slurry-based abrasive products.
One challenge with loose abrasive wire sawing is its dependence on the dispersibility of particles in solution and the integrity of the wire in heavy-duty cutting cycles. Fixed diamond wire sawing has been developed to succeed in these very issues.
Fixed diamond wire sawing utilizes an extremely thin steel cable impregnated with diamond particles using an electroplated nickel (Ni) or high-performance resin bonding agent. This combines all the established benefits of loose abrasive technologies, such as the extremely narrow kerf and excellent cut rates, with improved throughput and superior particle distribution. It also ensures minimal contamination of wafers to preserve the microstructural integrity of high-purity semiconducting systems.
Saint-Gobain is a world leader in industrial processing technologies for an expansive range of industries. We have developed a suite of products and services to assist in the development of the underlying intermediate goods of a range of demanding application areas.