Silicon Technology
In 2001, Ulysse Nardin’s revolutionary timepiece, the Freak, made history as the first watch to incorporate a silicon escapement, ushering in a new era of watchmaking.
The Silicon Manufacturing Process
Material preparation
Silicon is a metalloid, a type of chemical element that resembles metal without possessing all of its properties, in particular its hardness. The silicon used by Sigatec comes in the form of a wafer, a disc about 15 cm in diameter and only a few tenths of millimeters thick, carved out of a silicon crystal ingot produced synthetically by smelters. These ingots, which can measure up to two meters high, are made of a single crystal, ensuring a perfectly homogenous and high-quality material. The wafers are cut and polished to prepare them for the intricate etching process.
Deep Reactive Ion Etching (DRIE)
DRIE is a precise etching process performed in a cleanroom environment to ensure absolute precision. Wafers are coated in a photosensitive epoxy resin and exposed to UV light, which selectively radiates the photosensitive resin, through a photomask, therefore transferring the desired shapes onto the wafer.
Plasma and Ion Bombardment
What follows is the deep engraving phase, or etching. In two plasma machines, the wafer bearing the geometric shapes for the desired components is inserted. Within this confined tank, a near-total vacuum is maintained. Several fluids are introduced in succession. Through this succession of micro-layering, silicon reaches the desired thickness. To obtain complex multi-level pieces, several masks can be applied on the same wafer at different manufacturing stages. The wafers are removed from the plasma machine, irradiated through a new mask, and reinserted into the etching machine. Each geometry achieved boasts a precision of ±2 microns.
Final Treatment and Finishing
Once the wafer is etched, the remaining epoxy resin is meticulously removed. The process then enters its final stage. In an oven filled with gases and heated to precise, confidential temperatures, a layer of silicon dioxide forms on the surface of the components. This layer not only hardens the pieces but also achieves the desired stability in the face of thermal variations. At this stage, the components also take on their final coloring, with hues ranging from bright purple to slate grey. Optional monocrystalline diamond coatings, known as Diamonsil®, can be applied to the components.
Energy outcome
The DRIE process and other silicon manufacturing stages consume significant amounts of energy. To mitigate this, Sigatec has implemented a geothermal borehole system, reducing energy consumption and minimizing the environmental impact.