What do post-Moore devices look like?
Latest update time：2019-09-05
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As the semiconductor industry has developed to this day, Moore's Law has begun to weaken. Although some manufacturers are still insisting on making breakthroughs along the path of Moore's Law, there are also many voices in the industry that want to develop post-Moore's Law. In the development of post-Moore's Law, what will various electronic devices look like?
According to the International Semiconductor Roadmap, when the feature size is approaching the limit, new materials mainly based on wide bandgap semiconductors, carbon nanotubes, and two-dimensional layered materials, as well as new principles mainly based on tunneling transistors, negative capacitance transistors, and spin transistors have become the darlings of post-Moore devices.
Among them, how to apply two-dimensional layered materials to devices has been one of the research directions of scientific research institutions in recent years. In the construction of new material transistors, interface control (van der Waals heterogeneous integration and ultra-thin buffer layer) and physical property regulation (embedding and compounding) are required.
Some research institutes have stated that developing integrated technology of heterogeneous materials and multiple functional devices while maintaining the original device and process dimensions can achieve functional diversification of a single chip. Therefore, heterogeneous integration technology has begun to receive attention in the industry.
Among heterogeneous integration technologies, the development of van der Waals heterogeneous integration technology has attracted much attention from industry insiders. According to the Ministry of Information Science, due to the characteristics of no dangling bonds on the surface of two-dimensional layered materials, different two-dimensional atomic layers need to be stacked together in a selected order with the help of weak van der Waals forces to form an artificial heterostructure with an atomically flat interface. This heterostructure is usually called a van der Waals heterojunction. Compared with traditional integration methods, van der Waals heterogeneous integration will reduce damage to the material surface, thereby improving transistor performance.
At the same time, some organizations believe that although the van der Waals heterojunction has great potential, it is still some distance away from practical application at this stage. One of the main reasons is that devices based on van der Waals heterojunction have failed to fully utilize the advantages of two-dimensional layered materials, and most of their functions are relatively simple and their performance needs to be further improved.
As for the other aspect of interface control - the ultra-thin buffer layer, ozone was used to introduce an ultra-thin oxide layer on the surface of molybdenum disulfide, and high-quality HfO2 gate dielectrics (effective dielectric thickness EOT ~ 1 nm) were deposited, resulting in a top-gate transistor with the largest saturated output current density (612 μA/μm) at room temperature at that time.
According to a report from the Key Laboratory of Micro-Nano Optoelectronic Devices and Applications of the Ministry of Education at Hunan University, the use of van der Waals heterogeneous integration and ultra-thin buffer layer methods can suppress defects caused by traditional deposition techniques, reduce the interface defect density of gate dielectrics/two-dimensional materials, and weaken the pinning effect of metals/two-dimensional materials, thereby obtaining a high-quality device interface.
From the perspective of physical control, as far as the two-dimensional material itself is concerned. The valence bonds between atoms within the plane of the two-dimensional material are generally strong, and the use of conventional doping schemes to replace the atoms within the plane to control the physical properties of the material is often ineffective. The interlayer force of two-dimensional materials is mainly van der Waals force, and the interaction is weak. Therefore, scientific research institutions have proposed a method of embedding low-dimensional materials. That is, without changing the structure, atomic type and proportion of the two-dimensional material itself, only embedding and adsorbing other molecules, ions or low-dimensional materials between layers or on the surface, changing the interlayer spacing or surface electronegativity, so as to achieve the purpose of regulating the physical properties of the material.
Due to the interaction between layers, the energy bands and performance of two-dimensional materials are often related to the number of layers. The properties of a single layer are often the best, but the single layer interface has the greatest impact in the development of devices. How can we obtain a two-dimensional material structure (single layer properties) that is independent of the number of layers and obtain a uniform device? Research at Hunan University has shown that an artificial two-dimensional superlattice (MACMS) has been successfully realized by repeatedly stacking single-layer two-dimensional crystals/single-layer molecules, and an artificial two-dimensional black phosphorus atomic superlattice structure whose material properties are independent of the number of layers can be obtained.
From the development of two-dimensional layered materials, perhaps we can get a glimpse of what future post-Moore devices will look like.
At the 3rd Semiconductor Material Device Characterization and Reliability Research Exchange Conference of Tektronix, industry experts shared their research results in this area. To learn more about the development prospects of post-Moore devices,
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