The Future of Power Electronics – CHS Silicon Carbide
Like many technologies that came before them, power electronics are evolving to create next-generation models using a new semiconductor material known as silicon carbide (SiC). The market for SiC materials is booming, recently reflected by STMicroelectronics, a multinational electronics and semiconductor manufacturer, purchasing $120 million of advanced 150mm silicon carbide wafers to address the demand ramp-up for silicon carbide power devices. However, to meet demand for SiC wafers, manufacturers benefit from identifying cost-effective and commercially viable silicon precursors, such as the liquid form of silicon known as cyclohexasilane Si6H12 (CHS). CHS can do what other silicon precursor materials can not, deposit SiC films on semiconductor wafers with low defect densities and high structural quality, all at a lower operational cost. SiC semiconductors have represented a potential solution since the 1990s when NASA was first looking into them, but the complexity of these devices and challenges surrounding fabrication have limited their use. Now, the industry is looking to ramp up production of SiC power devices, and we believe CHS will play a key role in meeting this growing demand. What is the potential of SiC? SiC, specifically its β-SiC poly type, offers outstanding physical and chemical properties, making it a suitable material for low cost and high-quality thin films capable of large-scale deposition in power electronics. A large band gap and high breakdown voltage allow SiC to be utilized in 600 to 1200 V commercial-scale diodes and transistors. Additionally, the thermal stability of SiC allows high temperature sensors to be readily used. Why isn’t SiC more broadly used for Si Wafers? There are a few specific challenges to broader adoption of β-SiC for power electronic semiconductors. First, a suitable silicon precursor replacement for silane (SiH4) and other organosilicons, does not exist. Second, the chemistry of traditional β-SiC films is complicated by deformation, grain boundaries, and surface reactions at the SiC-Si interface, all of which can cause current leakage and plastic deformation of the material. How can CHS create a cost-effective Si precursor? CHS is a cost-effective silicon precursor for semiconductor devices and β-SiC thin films deposited on a variety of substrates under mild conditions including conventional and laser assisted CVD, LPCVD, and APCVD. CHS is unique in that it exists as a liquid at room temperature allowing for easier storage and handling. The growth rate of β-SiC using CHS is an order of magnitude faster than other silicon precursors and the crystalline quality rivals materials grown by molecular-beam epitaxy. Furthermore, CHS allows for facile p-doping of materials into the β-SiC films, and due to the methods of deposition amenable to a reagent such as CHS continuous growth without unintentional secondary deposits can be achieved. Combined, the benefits of CHS make it possible to deliver a high structural quality SiC at a lower cost. Silicon carbide is the future of power electronics, and CHS offers the potential to overcome the historic limitations of SiC semiconductor manufacturing in a cost effective manner. With the ability to deposit more silicon in thin films on a variety of substrates, this advanced material will unlock tremendous potential in our power electronics.