Challenges and opportunities of CMOS technology

     CMOS (also known as complementary metal oxide semiconductors) is an integrated circuit technology used to build digital, analog, and mixed-signal integrated circuits. It consists of two metal oxide semiconductor transistors, PMOS (positive metal oxide semiconductor) and NMOS (negative metal oxide semiconductor).

     CMOS In an interesting context of changing technology and product needs, creative combinations have spawned innovative solutions. The Apple M1 Ultra, for example, essentially stitches two AT25320B-SSHL-T chips together via a silicon bridge to create a hybrid SoC with unprecedented performance and functionality. AMD increased memory capacity by 3D stacking SRAM chips on top of the original processor SoC. In the field of artificial intelligence, super scale-out processing systems such as all-wafer Cerebras' WSE-2 and Nvidia's large GPU chip H100 combined HBM DRAM are pushing the boundaries of deep learning computing.

     CMOS technology has achieved great development and application in the past decades, and its comprehensive performance is superior to other integrated circuit technologies. CMOS technology has the advantages of low power consumption, strong anti-interference ability and low production cost. In addition, CMOS technology enables higher integration and larger interconnection than bipolar (BJT) technology.

     However, in CMOS scaling, a number of obstacles arise. First of all, when the transistor size is reduced to the nanometer level, there are a variety of physical effects, such as interconnect resistance, transistor leakage current, tunneling effect, etc., which will adversely affect circuit performance. Second, CMOS scaling leads to increased complexity and technical difficulty in circuit manufacturing, such as precisely controlling process parameters and reducing the variability between transistor layout/size.

     Therefore, in order to overcome the difficult problem of CMOS scaling, CMOS technology is gradually deepening downward and optimizing in collaboration with other technologies. For example, new materials such as high dielectric constant materials and metal gate alternatives are introduced. In addition, three-dimensional integrated circuits, layered structures, nanowires, etc., are also gradually applied to CMOS technology to improve integration and performance.

     Despite the challenges CMOS technology faces, it is still the mainstream technology for the next generation of chips. In the future, in order to meet the challenges of Moore's Law, CMOS technology will continue to evolve: first, continue to reduce the size of transistors, using new materials and structures to optimize circuit design; Secondly, more innovative technologies are introduced, such as quantum computing, spintronics, and optoelectronic integration. Finally, the software and hardware co-optimization is strengthened, and the efficient energy management and adaptive performance control at the system level are emphasized.

     In general, CMOS technology will continue to innovate in the face of challenges, introducing synergistically optimized solutions to ensure the development and application of chip technology.