1. Introduction Throughout the history of human civilization, all major changes in production and lifestyles have been triggered by new scientific discoveries and technologies. Science and technology, as a revolutionary force, have propelled human society forward. The development history from the invention of the transistor more than 50 years ago to the current foundation and core of microelectronics technology in the entire information society fully demonstrates that "science and technology are the primary productive force." Information is a universal form of the state and movement characteristics of objective things, and along with materials and energy, it is an important resource for human society, but its utilization is only just beginning. The current information revolution is characterized by digitization and networking. Digitization has greatly improved people's use of information and better met their information needs; while networking makes it easier for people to exchange information, turning the entire earth into a "global village." Information technology, characterized by digitization and networking, differs from general technology in that it has extremely strong pervasiveness and fundamental nature. It can penetrate and transform various industries and sectors, changing human production and lifestyles, and altering economic forms and various fields such as society, politics, and culture. One of its foundations is microelectronics technology. It is no exaggeration to say that without advancements in microelectronics technology, the booming development of information technology today would not have been possible; microelectronics has become the cornerstone of the entire information society. The history of microelectronics technology development over the past 50 years is essentially a process of continuous innovation, encompassing original innovation, technological innovation, and application innovation. The invention of the transistor was not an isolated, meticulously designed experiment, but rather the inevitable result of a series of major breakthroughs in solid-state physics, semiconductor physics, and materials science. The invention of the point-contact transistor in 1947, the junction field-effect transistor in 1948, and subsequent major inventions in microelectronics such as silicon planar technology, integrated circuits, CMOS technology, semiconductor random access memory, CPUs, and non-volatile memory are all manifestations of a series of innovative achievements. Simultaneously, each major invention has opened up a new field, brought new and enormous markets, and had a significant impact on our production and lifestyles. It is precisely because of continuous innovation in the field of microelectronics technology that microelectronics has been able to develop for decades at a rate of doubling integration density and shrinking feature sizes every three years. Since 1968, the number of academic papers related to silicon technology has surpassed that related to steel. Therefore, some argue that after 1968, humanity entered the silicon age, following the Stone Age, Bronze Age, and Iron Age [1]. Thus, it can be said that the essence of social development is innovation; without innovation, society can only be imprisoned in a "super-stable state" trap. Although innovation, as a driving force for economic development, often brings "creative destruction" to society, after this destruction, a new, higher-level innovation cycle will begin, and society develops forward in this spiral-like upward trajectory. In the first 50 years of microelectronics technology development, innovation played a decisive role, and the future development of microelectronics technology will still depend on the emergence of a series of innovative achievements. We believe that microelectronics technology has reached a critical juncture. The development trends and major innovation areas of microelectronics technology in the first half of the 21st century, that is, the next 50 years, mainly fall into four categories: silicon-based CMOS circuits as the mainstream process; System-on-a-Chip (SOC) as the development focus; quantum electronic devices and nanoelectronics based on molecular (atomic) self-assembly technology; and the emergence of new technological growth points through integration with other disciplines, such as MEMS and DNA Chips. 2. Silicon-based CMOS circuits will remain the mainstream process in the first half of the 21st century. The goal of microelectronics technology development is to continuously improve the performance and price-performance ratio of integrated systems. Therefore, it requires increasing the integration density of chips, which is the driving force behind the continuous reduction of semiconductor device feature sizes. Taking MOS technology as an example, reducing the channel length can increase the speed of integrated circuits; at the same time, reducing the channel length and width can also reduce the device size and increase the integration density, thereby integrating more transistors on a chip, integrating more complex and higher-performance electronic systems onto a single chip; in addition, with the increase in integration density, the speed and reliability of the system are greatly improved, and the price drops significantly. Since the delay of the on-chip signal is always less than the delay of the inter-chip signal, the performance of the entire integrated system can be greatly improved even if the performance of the device itself is not improved after the device size is reduced. Since the invention of integrated circuits in 1958, in order to improve the performance of electronic systems and reduce costs, the feature size of microelectronic devices has been continuously reduced, the processing precision has been continuously improved, and the area of ​​silicon wafers has been continuously increased. The development of integrated circuit chips basically follows Moore's Law, which was predicted by Gordon E. Moore, one of the founders of Intel Corporation, in 1965. That is, every three years the integration density increases by 4 times and the feature size decreases by 10 times. During this period, although many people predicted that this development trend would slow down, the development of the microelectronics industry over the past 30 years has confirmed Moore's prediction [2]. Moreover, according to our prediction, this development trend of microelectronics technology will continue for a period of time in the 21st century, which is unmatched by any other industry. Currently, 0.18-micron CMOS technology has become the mainstream technology in the microelectronics industry. Devices with a feature size of 0.035 microns and even 0.020 microns have been successfully fabricated in laboratories, and research has entered the sub-0.1-micron technology stage, with corresponding gate oxide layer thicknesses of only 2.0–1.0 nm. It is expected that by 2010, 64G DRAM products with feature sizes of 0.05–0.07 microns will be put into mass production. In the 21st century, at least in the first half of the 21st century, microelectronics manufacturing technology will still be dominated by silicon-based CMOS technology with continuously shrinking dimensions. Although significant progress has been made in the research of microelectronics compounds and other new materials, they are not yet ready to replace silicon-based processes. According to the laws of scientific and technological development, it generally takes 20 to 30 years for a new technology to go from its inception to becoming a mainstream technology. Silicon integrated circuit technology, from the invention of the transistor in 1947 to the invention of the integrated circuit in 1958, also took more than 20 years to develop into a major industry by the end of the 1960s. Furthermore, trillions of dollars invested in equipment and technology worldwide have enabled silicon-based processes to form a very strong industrial capability. Simultaneously, long-term research investment has resulted in a profound and thorough understanding of the various properties of silicon and its derivatives, making it the most comprehensive among the more than 100 elements in nature—a truly invaluable accumulation of knowledge. This industrial capability and knowledge accumulation determine that silicon-based processes will continue to play a crucial role for at least the next 50 years, and will not be easily abandoned. Currently, many believe that the era of silicon technology will end when the feature size of microelectronics reaches its "limit" of 0.030–0.015 micrometers in 2015. This is actually a misunderstanding. Not to mention that microelectronics technology, besides processing technology represented by feature size, also requires further development in design technology and system architecture, and the development of these technologies will inevitably lead to continued rapid growth in the microelectronics industry. Even regarding processing technology, many renowned microelectronics experts predict that the microelectronics industry will enter a more mature, sunrise industry like the automotive and aerospace industries around 2030. Even as the microelectronics industry expands into mature industrial sectors like automobiles and aerospace, it will maintain a rapid growth trend, just as the automobile and aerospace industries, despite over 50 years of development, still possess immense growth potential. As device feature sizes shrink, a series of challenges inevitably arise regarding device structure, key processes, integration technologies, and materials. The main reasons for this are: our understanding of the underlying physical laws and scientific issues remains rooted in classical or semi-classical theories developed in the early days of integrated circuits. These theories are suitable for describing microelectronic devices at the micrometer scale, but are less applicable to new devices in system-on-chips with spatial scales at the nanometer and femtosecond levels; in terms of materials, traditional materials such as SiO2 gate dielectric and polysilicon/silicide gate electrodes, constrained by their material properties, can no longer meet the demands of sub-50nm devices and circuits; simultaneously, traditional device structures are also insufficient for sub-50nm devices, necessitating the development of novel device structures and key process technologies such as microfabrication, interconnection, and integration. Specific areas requiring innovation and key development include: transport theory, device models, simulation and simulation software for semiconductor devices based on mesoscopic and quantum physics, novel device structures, high-k gate dielectric materials and novel gate structures, electron beam stepping lithography, 13nm EUV lithography, ultra-fine line etching, novel circuits compatible with silicon-based processes such as SOI and GeSi/Si, low-k dielectrics and Cu interconnects, and the fabrication and integration technologies of quantum devices and nanoelectronic devices. 3. Quantum electronic devices (QED) and nanoelectronics based on molecular atom self-assembly technology will bring new fields. In the previous section, we discussed silicon-based CMOS process technology with continuously shrinking dimensions, which can be called "scaling down". At the same time, we must pay attention to "bottom up". The most important areas of "bottom up" are two aspects: (1) Quantum electronic devices (QED) This includes single-electron devices and single-electron memories. Its basic principle is based on the Coulomb blocking mechanism to control the movement of one or more electrons. Due to the change in system energy and the Coulomb effect, an electron enters a potential well, which will prevent other electrons from entering. In single-electron memory, quantum wells replace floating gates in ordinary memory. Its main advantages are high integration density; extremely low power consumption due to only one or a few electrons in operation; high speed due to relatively small capacitance and resistance and short tunneling time; and it can be used for multi-valued logic and ultra-high frequency oscillation. However, its problems are that it is difficult to manufacture, especially the manufacture of a large number of consistent devices; it is highly sensitive to the environment and its reliability is difficult to guarantee; it requires extremely small capacitance (αF) when operating at room temperature and requires quantum dot size to be a few nanometers. These all bring great difficulties to the integration into circuits. Therefore, it can be considered that their theory is clear at present, but the process needs to be explored and broken through. (2) Nanoelectronics based on atomic and molecular self-assembly technology. This includes quantum dot arrays (QCA) and atomic and molecular devices based on carbon nanotubes. Quantum dot arrays are composed of quantum dots, at least four quantum dots, which interact with each other by electrostatic force. The quantum dots are categorized into "0" and "1" states based on the state of electrons occupying them. Essentially, it's a non-transistor, wireless method to achieve high density, low power consumption, and interconnectivity in arrays. Its fundamental advantages are fast switching speed, low power consumption, and high integration density. However, it is difficult to manufacture and extremely sensitive to changes in position and size; a change of 0.05 nm can cause cell malfunction. Carbon nanotube-based atomic and molecular devices are a promising field that has seen rapid development in recent years. The strong bonding between carbon atoms supports high-density currents, while its thermal conductivity is similar to diamond, significantly reducing heat dissipation at high integration levels. Its properties are similar to metals and semiconductors, especially its three possible hybrid states, while Ge and Si only have one. These factors make carbon nanotubes (CNTs) a current research hotspot. Since their discovery in 1991, numerous achievements have emerged. Professor Peng Lianmao of the Peking University Nanotechnology Center has also fabricated 0.33 nm CNTs and proposed the possibility of using "T-junctions" as transistors. However, the challenge lies in growing ordered CNT devices that meet design performance requirements, and even more so in integration. Currently, bottom-up quantum devices and nanodevices based on self-assembly technology are often manufactured using scaling-down methods. This will bring breakthrough progress in solving the power consumption constraints of highly integrated CMOS circuits. QCA and CNT devices still require significant work in both theory and fabrication technology, and breakthroughs are yet to be achieved; practical applications will take considerable time. However, this is ultimately an attractive field to explore, and we anticipate they will create a new world. 4. System-on-a-Chip (SoC) is a key focus of 21st-century microelectronics development . In the early stages of integrated circuit (IC) development, circuit design began with the physical layout of devices. Later, cell libraries emerged, allowing IC design to move from the device level to the logic level. This design approach enabled a large number of circuit and logic designers to directly participate in IC design, greatly promoting the development of the IC industry. However, an integrated circuit is only a semi-finished product; it only functions when integrated into a complete system. IC chips are used to realize complete systems through technologies such as printed circuit boards (PCBs). Although ICs can achieve high speeds and low power consumption, the performance of the entire system is significantly limited by factors such as interconnection delays between IC chips on the PCB, PCB reliability, and weight. As systems evolve towards higher speeds, lower power consumption, lower voltages, multimedia, networking, and mobility, the demands on circuitry are increasing, and traditional integrated circuit design technology can no longer meet the requirements of these increasingly demanding systems. Simultaneously, advancements in IC design and manufacturing technology have led to larger and more complex integrated circuits, enabling the integration of entire systems onto a single chip. Currently, it is possible to integrate 10⁸ to 10⁹ transistors on a single chip. Furthermore, with the development of microelectronics manufacturing technology, 21st-century microelectronics will gradually evolve from the current 3G era to the 3T era (i.e., storage capacity increasing from Gbit to Tbit, integrated circuit device speed from GHz to THz, and data transmission rate from Gbps to Tbps; note: 1G=10⁹, 1T=10¹², bps: bits of data transmitted per second). Driven by both demand and technology, the concept of System-on-a-Chip (SOC), which integrates the entire system onto a single microelectronic chip, emerged. The design philosophy of SOC differs from that of Integrated Circuits (ICs). It represents a revolution in microelectronics design, and its relationship with ICs is similar to that of ICs with discrete components at the time. Its impact on microelectronics technology is no less significant than that of IC technology, which rapidly developed from the late 1950s. SOC takes a holistic approach, tightly integrating processing mechanisms, model algorithms, chip structure, circuitry at various levels, and even device design. It completes the entire system's functionality on a single (or a few) chip, and its design must be top-down, starting from the system's behavioral level. Many studies have shown that compared to systems composed of ICs, SOC design, by comprehensively considering all aspects of the system, can achieve higher system performance under the same technological conditions. For example, if a system chip is designed using the SOC method and 0.35μm process, under the same system complexity and processing speed, it can achieve the same system performance as an IC made using 0.18-0.25μm process. In addition, compared with the chip designed using the conventional IC method, the number of transistors required to complete the same function using the SOC design method can be reduced by about 1 to 2 orders of magnitude. For the development of system chips (SOC), there are three key supporting technologies. (1) Software and hardware co-design technology. Functional partition theory for software and hardware of different systems. Here, different systems involve many computer systems, communication systems, data compression and decompression and encryption and decryption systems, etc. (2) IP module library problem. There are three types of IP modules: soft core, which is mainly functional description; hard core, which is mainly structural design; and hard core, which is based on process physical design, process-related, and verified by process. Among them, hard core has the highest use value. CMOS CPU, DRAM, SRAM, E2PROM and Flash Memory, as well as A/D, D/A, etc. can all be hard cores. Among them, the most valuable are modules based on new device models and circuit simulations in deep submicron, which are optimized in terms of speed and power consumption and have the largest process tolerance. Now, based on the fabless companies that emerged in Silicon Valley in the 1980s, some chipless companies emerged in the late 1990s, specializing in the sale of IP modules. (3) Comprehensive analysis technology between module interfaces, which mainly includes glue logic technologies between IP modules and comprehensive analysis and implementation technology of IP modules. The transformation of microelectronics technology from IC to SOC is not only a conceptual breakthrough, but also a milestone in the new development of information technology. Through the innovation of the above three supporting technologies, it will inevitably lead to another revolution in information technology based on system chips. At present, SOC technology has emerged, and the 21st century will be the period of rapid development of SOC technology. In the field of next-generation system chips, the key innovation points that need to be broken through mainly include the two aspects of algorithms and circuit structures for realizing system functions. In the history of microelectronics development, every algorithm has sparked a revolution. For example, the Viterbi algorithm and wavelet transform have played crucial roles in the development of integrated circuit design technology. Currently, neural networks and fuzzy algorithms are also likely to achieve significant breakthroughs. While proposing a new circuit structure can drive a series of applications, proposing a new algorithm can drive a new field. Therefore, algorithms should be one of the key research disciplines in the future system-on-a-chip (SoC) field. Regarding circuit structure, due to the addition of radio frequency and memory devices, the circuit structure in SoCs is no longer the traditional CMOS structure, thus requiring the development of more flexible new circuit structures. Furthermore, to realize glue-connected logic, new logic array technology is expected to develop rapidly, and in-depth systematic research is also needed in this area. 5. The Combination of Microelectronics with Other Disciplines Creates New Technological Growth Points The powerful vitality of microelectronics technology lies in its ability to produce high-reliability and high-precision microelectronic structure modules at low cost and in large quantities. Once this technology is combined with other disciplines, it will give rise to a series of new disciplines and significant economic growth points. Typical examples of this are MEMS (Micro-Electro-Mechanical Systems) technology and DNA biochips. The former (microelectronics) arose from the combination of microelectronics with mechanics, optics, and other fields, while the latter (microelectromechanical systems) is a product of the combination with bioengineering. Microelectromechanical systems (MEMS) are not only an extension and expansion of microelectronics technology, but also a fusion of microelectronics and precision machining technology, achieving a system where microelectronics and mechanics are integrated. MEMS connects electronic systems to the external world; it can not only sense external signals from nature such as motion, light, sound, heat, and magnetism, converting these signals into electrical signals that the electronic system can understand, but also control these signals through the electronic system, issuing and executing commands. Broadly speaking, MEMS refers to a micro-electromechanical system integrating micro-sensors, micro-actuators, signal processing and control circuits, interface circuits, communication systems, and power supplies. MEMS technology is a typical multidisciplinary, cutting-edge research field, involving almost all areas of natural and engineering sciences, such as electronics, mechanics, optics, physics, chemistry, biomedicine, materials science, and energy science. The development of MEMS has opened up a completely new technological field and industry. They can not only reduce the cost of electromechanical systems, but also accomplish many tasks that large-scale electromechanical systems cannot. MEMS devices and systems possess unparalleled advantages over traditional sensors, including small size, light weight, low power consumption, low cost, high reliability, excellent performance, and powerful functionality. Therefore, MEMS has a very broad application prospect in aviation, aerospace, automotive, biomedicine, environmental monitoring, military, and almost every field people encounter. For example, micro-inertial sensors and their constituent micro-inertial measurement units can be applied to guidance, satellite control, autonomous driving, automotive airbags, anti-lock braking systems (ABS), stability control, and toys; micro-flow systems and micro-analyzers can be used for micro-propulsion and casualty rescue; information MEMS systems will play a significant role in radio frequency systems, all-optical communication systems, high-density memory, and displays; MEMS systems can also be used in medicine, spectral analysis, information acquisition, and more. Currently, miniature tweezers with a tip diameter of 5μm, capable of holding a red blood cell, and butterfly-sized airplanes that can fly in magnetic fields have been successfully manufactured. MEMS technology and its products are growing at a very high rate and are currently in a period of technological development. In a few years, we will see a period of rapid industrialization for MEMS. In 2000, the global MEMS market reached $12-14 billion, with related markets reaching $100 billion. Currently, the development of MEMS systems is remarkably similar to the early stages of integrated circuit development. In the early days of integrated circuit development, circuits were remarkably simple, with very limited applications, primarily driven by military needs. However, their promising prospects attracted substantial investment, propelling the rapid development of integrated circuits. Advances in integrated circuit technology accelerated the pace of computer upgrades, increasing the demand for CPUs and RAM, which in turn further fueled the development of integrated circuits. Integrated circuits and computers mutually reinforced each other's development, creating today's win-win situation and bringing about an information revolution. Currently, MEMS are highly specialized, with very limited applications for individual systems; products with the widespread adoption of CPUs and RAM have not yet emerged. With further advancements in MEMS, it is possible that a new industry with broad application prospects, similar to microelectronics technology, will eventually emerge, significantly impacting people's social production and lifestyles. Whether MEMS systems can achieve greater breakthroughs depends on two factors: First, breakthroughs in microsystem theory and fundamental technologies, enabling the efficient design and manufacture of required microsystems based on mastered theories and fundamental technologies; second, identifying application breakthroughs, leveraging strengths and avoiding weaknesses, and focusing research on major areas particularly suitable for microsystem applications to achieve breakthroughs and drive the development of the microsystem industry. Key issues that need to be addressed in the development of MEMS include: MEMS modeling and design methodology research; principles, methods, simulation, and manufacturing of three-dimensional microstructures; microscale mechanics and thermodynamics research; MEMS characterization and metrology methodologies; and nanostructure and integration technologies. Biochips, represented by DNA chips, born from the close integration of microelectronics and biotechnology, will be another hot topic and new economic growth point in the 21st-century microelectronics field. Based on biological science, they utilize the characteristics and functions of organisms, tissues, or cells to design and construct new species or strains with expected traits, and combine this with engineering technology for processing and production. They are a product of the integration of life sciences and technological sciences, possessing characteristics such as high added value and low resource consumption, and are increasingly attracting widespread attention. Currently, the most representative biochip is the DNA chip. Using microelectronics fabrication technology, chips containing up to tens of thousands of DNA gene fragments can be fabricated on a silicon wafer the size of a fingernail. These chips can detect or identify changes in genetic material in a very short time, which undoubtedly plays a crucial role in genetic research, disease diagnosis, disease treatment and prevention, and transgenic engineering. The basic idea of ​​DNA chips is to use biological reactions or the application of an electric field to make certain substances reflect the characteristics of a specific gene, thereby achieving the purpose of gene detection. Researchers at Stanford and Affymetrix have already fabricated DNA chips on silicon or glass wafers using microelectronics technology [4]. Their DNA chips are created by etching very small grooves into a glass wafer and then covering these grooves with a layer of DNA fibers. Different DNA fiber patterns represent different DNA gene fragments; the chip contains more than 6,000 DNA gene fragments. DNA (deoxyribonucleic acid) is one of the most important substances in biology, containing a vast amount of biological genetic information. DNA chips play a crucial role and have a wide range of applications: they can be used not only in genetic research and biomedicine, but also, with the development of DNA chips, will form microelectronic bioinformatics systems. This technology will then be widely applied to all aspects of human life, including agriculture, industry, medicine, and environmental protection. At that time, biochips may be as ubiquitous as IC chips are today. Currently, biochips mainly refer to microanalytical units and systems constructed on the surface of solid chips using planar microfabrication technology and supramolecular self-assembly technology to achieve accurate, rapid, and high-information screening or detection of compounds, proteins, nucleic acids, cells, and other biological components. The main research areas of biochips include the specific implementation technologies of biochips, bioinformatics based on biochips, and the design and detection methodologies of high-density biochips. 6. Conclusion In the first 50 years of the development of microelectronics, innovation and basic research played a crucial and decisive role. With the shrinking of device feature sizes, the emergence of nanoelectronics, the development of next-generation SOCs, and the rise of MEMS and DNA chips, a series of new challenges have arisen, and objective demands are calling for the birth of innovative achievements. Looking back at the last 50 years of the 20th century and looking forward to the first 50 years of the 21st century—a century of development in microelectronics science and technology—we deeply feel that the turn of the century presents both a significant opportunity and a severe challenge for us. If we can seize this opportunity, focus on innovation, and bravely meet this challenge, it is possible for my country's microelectronics technology to take off, possess its own intellectual property rights in next-generation microelectronics technologies, promote the development of my country's microelectronics industry, lay the technological foundation for the great national rejuvenation that will arrive in the mid-21st century, and ultimately rebuild the glory of the Chinese nation!