Best methods for atomic-level cleaning of semiconductor interfaces

In semiconductor manufacturing, atomic-level defects and contamination pose significant challenges to the performance, reliability, and yield of devices. From high-precision sensors to powerful processors, even the smallest impurity can impact the functionality of semiconductor products. To mitigate these issues, several advanced cleaning techniques are employed to purify interfaces and ensure high-quality results. In this post, we’ll explore the most common atomic-level cleaning methods, their benefits and disadvantages, and discuss how the latest advancements can complement these widely utilized methods for an optimized cleaning process.

1. High-purity semiconductor materials and ultra-high purity precursors (CVD/MBE)

Chemical Vapor Deposition (CVD) and Molecular Beam Epitaxy (MBE) are used to deposit thin films of semiconductor materials at atomic precision. The key to success in these processes is the use of high-purity materials and ultra-high-purity precursors to minimize contamination during film growth.

The methods provide plenty of benefits: By using high-purity materials, the films produced are less likely to contain impurities, ensuring better electrical and structural properties. Both CVD and MBE allow for precise layer thickness control, which is crucial for producing devices with exceptional performance, such as transistors and diodes. These processes offer precise control over doping and the creation of complex multi-layer structures, which are important for advanced semiconductor applications like 3D integrated circuits and high-performance microchips.

On the other hand, high-purity materials and specialized equipment needed for CVD and MBE increase complexity and can drive up manufacturing costs. These processes are typically slow and may not be ideal for mass production where speed is critical.

The processes are ideal for specialty materials and high-performance components. They are also often used in LEDs and laser diodes, where purity is crucial for efficiency. In the creation of quantum devices with very high precision, they can be deemed necessary.

2. Specialized chemical solutions for contaminant removal

Using chemical solutions to remove contaminants from the wafer surface is one of the most common and effective ways to clean silicon wafers. Acidic or basic solutions can remove organic and inorganic residues, such as oils, dust, and particulate matter.

They can quickly and efficiently remove a wide range of contaminants, including organic residues, dust, and particulates that may not be removed by simple rinsing. These chemical solutions are also scalable and can be used in high-throughput environments, making them suitable for mass production. Generally, chemical cleaning is more cost-effective compared to other advanced methods like MBE or ALD.

There are also disadvantages related to using chemical solutions. If not done carefully, chemical residues can remain on the wafer, introducing new contamination. While effective at cleaning surfaces, these methods may not provide atomic-level precision, especially for intricate or highly sensitive devices.

Chemical cleaning is used widely in semiconductor fabs for cleaning before and after deposition. It is ideal for applications that don’t require extreme precision, such as industrial sensors and low-cost components.

3. Plasma Cleaning for Organic Residues and Atomic-Level Impurities

Plasma cleaning uses ionized gases (plasma) to remove organic residues and atomic-level impurities from surfaces. Plasma treatment can clean silicon, metal, and polymer surfaces by ionizing gases such as oxygen or nitrogen.

Plasma cleaning is excellent for removing organic contaminants, especially when dealing with delicate electronic devices. Plasma can be used to modify the surface of the materials to enhance adhesion or promote bonding. The process does not physically touch the wafer, minimizing the risk of damage during cleaning.

However, overexposure to plasma can damage sensitive layers or alter surface characteristics, potentially reducing the performance of the semiconductor. While effective against organic materials, plasma cleaning may not remove inorganic contaminants as effectively.

The solutions are often used in LEDs, solar cells, and photodetectors, where organic contamination needs to be cleaned from delicate surfaces. Plasma cleaning can be also used to prepare surfaces for MEMS (Micro-Electro-Mechanical Systems) fabrication.

4. Atomic Layer Deposition (ALD) for Conformal Coatings and Surface Passivation

ALD is an advanced deposition technique that creates ultra-thin, highly uniform films at the atomic level. It is especially valuable in creating passivation layers on semiconductor surfaces, effectively sealing surfaces and interfaces against contamination.

ALD allows for precise control of film thickness on a layer-by-layer basis, which ensures conformal coatings even on complex geometries. It is ideal for passivating semiconductor surfaces, reducing defects and enhancing device longevity. ALD provides highly uniform coatings, essential for high-performance devices.

There are certain disadvantages related to ALD: ALD is slower than some other deposition techniques and may not be suitable for high-throughput manufacturing. In addition, the materials used in ALD can be costly, making it less suitable for mass production of lower-end devices.

ALD is used in advanced semiconductor nodes, memory chips, and power devices.  It is ideal for sensitive optical coatings in laser diodes and LEDs. In quantum computing and nanoelectronics, requiring atomic-level precision, it is frequently used.

Latest advancements in atomic-level cleaning

In recent years, fuelled by the narrowed line widths in semiconductor components and overall quest for better chip performance, new and more effective atomic-level cleaning methods have emerged. For example, SisuSemi’s atomic-level cleaning technology provides a complementary solution to the above-mentioned methods, offering distinct advantages:

• Atomic-Level Purity: While CVD, MBE, and ALD provide great precision for material deposition, SisuSemi focuses on ensuring that the material substrates used in these processes are free from contaminants at the atomic level, ensuring optimal film deposition.

• Enhanced Performance: For processes like plasma cleaning and chemical solutions, SisuSemi can improve their effectiveness by ensuring that the surfaces being cleaned are free of deep-seated contaminants, which enhances overall cleaning efficiency.

• Improved Yield: Sisusemi's cleaning technology can be applied before these processes to ensure higher first-pass yield and reduced defects, making it an ideal pre-treatment step before ALD, CVD, and MBE deposition.

In short, Sisusemi’s solution can be seamlessly integrated with existing semiconductor fabrication processes (such as ALD, MBE, and plasma cleaning) to ensure a cleaner, more efficient workflow, leading to higher-quality semiconductor devices, particularly in applications where precision and reliability are critical.

Conclusions

The semiconductor industry’s relentless demand for high-performance, reliable, and cost-effective devices makes the role of atomic-level cleaning techniques more crucial than ever. While methods like CVD, MBE, plasma cleaning, and ALD each offer unique benefits for deposition and cleaning, Advanced, novel technologies like SisuSemi’s solution ensures that substrates remain free from atomic-level contaminants, enhancing these processes and resulting in better yield, performance, and long-term device reliability.