Why is the 7-nanometer Wafer Fabrication Process So Difficult?

 

What is the 7nm process?

Before we talk about the 7nm process, let's understand what "nano" means. A nanometer (nm) is a unit of length, and 1 nanometer is equal to 10 to the minus ninth power. In the case of semiconductor chips, nanometer usually refers to the smallest size of a transistor, or the smallest structural size that makes up the individual functional units in a chip. Therefore, the 7nm process refers to the fabrication of a transistor with a minimum structure of 7 nm on a chip.

As transistors continue to shrink in size, chip integration, computing speed, and energy efficiency have increased dramatically. However, the realization of these technological breakthroughs is not smooth sailing, but requires solving a series of technical problems from design to materials, processes to manufacturing.

0040-09963 PEDESTAL,150MM FLAT,IS,NI LIFT2,HVCEN

0021-20572 PEDESTAL, 6 ADV.101 FULL CVRG

 

Why is it so difficult to break through the 7nm process?

Breaking through the difficulties of the 7nm process can actually be disassembled in multiple dimensions. To better understand it, let's compare it to building an increasingly sophisticated, complex, and efficient machine. Imagine you're trying to make a high-precision clock, where every gear and part has to be so small and precise that even the error of every detail can cause the overall function to fail. For the semiconductor manufacturing process, the 7nm process is just such a extreme challenge.

1. The approximation of physical limits

As transistor sizes continue to decrease, some physical limits have been approached. As soon as the size of the transistor is less than 10 nanometers, the quantum effect begins to manifest. For example, electrons exhibit quantum tunneling in these tiny transistors, where electrons can pass through the transistor's "well", causing current to leak, affecting the chip's performance and power consumption.

To overcome these issues, chip designers need to rely on innovative technologies, such as the use of higher-quality materials (e.g., high dielectric constant materials) or more advanced transistor structures (e.g., FinFETs). However, the introduction of these technologies is not a simple upgrade, but faces significant challenges in materials, manufacturing, and engineering.

2. The challenges of lithography

Lithography is one of the most critical aspects of the semiconductor manufacturing process. Photolithography is the process of projecting a design pattern onto a light-sensitive material on a silicon wafer to characterize the structure of a chip. However, as transistor sizes continue to shrink, traditional lithography techniques such as deep ultraviolet lithography (DUV) are unable to meet such delicate manufacturing needs.

To solve this problem, extreme ultraviolet lithography (EUV) technology has been introduced, which enables the use of shorter wavelengths of light, resulting in improved lithography accuracy. However, EUV technology itself faces many problems: first, EUV light sources are difficult to develop and require higher power to achieve sufficient exposure; Secondly, the imaging accuracy of the EUV exposure process has very high requirements for the equipment, and the research and development of photoresist materials is also in continuous progress.

Therefore, breakthroughs in lithography technology require not only advanced equipment support, but also multidisciplinary collaboration in materials science, optics and other fields.

3. Challenges in material and device design

With the advancement of the 7nm process, it is difficult to meet the requirements of high efficiency by relying solely on silicon materials. The limitations of materials science have forced us to consider alternative materials, such as high-k materials as well as new semiconductor materials such as gallium nitride, carbon nanotubes, etc. These new materials have the potential to improve chip performance, but their compatibility, stability, and integration with existing production processes remain challenges.

In addition, the 7nm process requires very short gate lengths for transistors, which places higher demands on the design of the device. Designers need to precisely control the size and layout of each device to avoid problems such as current leakage and excessive thermal effects due to errors.

4. Manufacturing precision and cost control

Manufacturing chips with 7nm processes requires ultra-high-precision equipment and processes. For example, processes such as the processing of silicon wafers, the deposition of thin films, etching all require extremely high precision, which places extremely demanding demands on production equipment. In addition, due to the extremely small size of the transistors in the 7nm process, even the smallest manufacturing errors can lead to a significant degradation of the performance of the entire chip, so every step of the production process must be strictly controlled.

The high precision requirements in the manufacturing process and the complex process chain mean a significant increase in costs. For example, the use of EUV lithography requires more expensive equipment and has a low yield rate of manufacturing, which can easily lead to defects during production, resulting in scrapped chips.

5. Power consumption and thermal management issues

As chips get smaller and smaller, the number of integrated transistors increases, and each transistor still consumes power. As the number of transistors increases, the problem of power consumption gradually becomes apparent. While the 7nm process is more energy efficient than the traditional process, the power management of the various parts within the chip has become more complex.

In addition, power consumption is closely related to heat, and when the heat inside the chip cannot be effectively dissipated, it may cause the chip to overheat, which can affect performance or even burn the device. Therefore, how to design an efficient thermal management system to avoid the thermal effects caused by excessive power consumption is also one of the key issues faced by the 7nm process.

Solutions & Future Developments

Despite the many challenges of breaking through the 7nm process, the semiconductor industry has already made initial breakthroughs with several innovative solutions:

Extreme ultraviolet lithography (EUV): EUV lithography is maturing and will become the primary technology for smaller process nodes such as 5nm, 3nm and even smaller in the future.

Three-dimensional integrated circuits (3D ICs): In order to break through the physical limits of plane layouts, many semiconductor companies have begun to research three-dimensional integrated circuit (3D IC) technology, which further improves the integration and performance of chips by vertically stacking transistors, memories and other components.

New semiconductor materials: In addition to silicon, the industry is also exploring other new semiconductor materials, such as carbon nanotubes, graphene, etc., to address the physical limitations encountered by traditional silicon materials in the process of size reduction.

Quantum computing: While quantum computing is still some way from being widely adopted, it is expected to break the bottleneck of traditional silicon-based computing as a potential alternative to future computing architectures.

Conclusion

The difficulty of breaking through the 7nm process is not only a breakthrough at the technical level, but also involves the comprehensive application of multiple disciplines such as materials science, physics, chemistry and engineering.