Researchers from Barcelona have found a way to more quickly and cheaply manufacture flexible thin crystalline silicon wafers.
Thin crystalline silicon wafers measuring around 10µm are costly to produce but also in increasing demand in microelectronics, due to the trend towards 3D circuit integration.
As the demand for ever thinner crystalline silicon wafers grow, techniques have been developed to yield wafers at these dimensions from monocrystalline cylindrical ingots.
Manufacturers used a multithreaded saw impregnated with abrasive material to cut layers from the ingots. However, these have a minimum thickness of around 150 µm.
Thinner wafers can be complicated to produce. Existing methods only allow such wafers to be obtained one at a time, and 50 percent of the silicon is lost in the process.
The research from the scientists at the Nanoengineering Research Centre (CRNE) and the Department of Electronic Engineering at the Universitat Politècnica de Catalunya • BarcelonaTech, allows a large number of crystalline layers, controlled for thickness, to be produced from a single crystalline silicon wafer in just a single step.
The scientists make small pores in the material and apply a high temperature during the manufacturing process.
By controlling the pore profiles, it is possible to obtain multiple separate crystalline silicon wafers. Pore diameters affect both the number of layers and their thickness.
The silicon layers are then separated by exfoliation. The resulting number of silicon layers is determined by the thickness of the layers themselves and the initial thickness of the wafer.
From a single 300mm thick wafer, the researchers succeeded in creating up to ten 5-7mm thin wafers.
Further scaling down of this method may allow relatively easy and fast creation of micron-scale thick silicon wafers by precision control of pore sizes.