RCA Cleaning: Challenges at the Atomic Scale in Semiconductor Fabrication and How SisuSemi's Ultra-High-Vacuum Technology Can Help

In semiconductor fabrication, cleanliness is extremely important — a single particle or impurity can cause major defects, impacting the performance and yield of the final chip. One commonly used cleaning method is RCA cleaning, a chemical process designed to remove contaminants from wafers before further processing. However, as semiconductor nodes shrink, the very cleaning techniques that are supposed to ensure pristine surfaces can themselves introduce challenges, particularly at the atomic scale.

In this blog post, we'll explore the challenges posed by RCA cleaning, its effects on the fabrication process and how SisuSemi’s innovative solution — leveraging low-power, ultra-high-vacuum technology — can resolve these atomic-level impurity issues, ultimately improving chip performance, quality, energy efficiency and yield.

RCA cleaning and its challenges

RCA cleaning is a widely used process in semiconductor manufacturing that involves a mixture of deionized water, hydrogen peroxide (H₂O₂) and ammonium hydroxide (NH₄OH) to remove organic contaminants, metals and particulate matter from wafer surfaces. While effective for cleaning, RCA cleaning introduces several risks at the atomic scale:

1. Atomic-level contamination:
   The chemicals used in RCA cleaning can leave behind trace impurities — especially metals or residual chemicals — that are not easily removed. Even microscopic levels of contamination can dramatically affect the subsequent fabrication steps, particularly at advanced nodes where features are measured in nanometers.

2. Surface damage:
   The aggressive chemical treatment can sometimes damage the wafer’s surface, creating atomic-level defects. These defects can be in the form of etching irregularities or changes in the material structure, making it more difficult to achieve precise patterning during the lithography phase.

3. Chemical residue:
   If the RCA cleaning process is not perfectly executed, residual chemicals or watermarks can remain on the wafer surface. These residues can lead to poor adhesion of photoresist layers, contamination during deposition or failure in critical etching steps.

How these defects and contaminants affect other phases of chip fabrication

The impurities left behind by RCA cleaning can have a cascading effect on subsequent stages of chip manufacturing. Here’s how atomic-level defects and contamination impact the process:

1. Lithography:
   As previously discussed, lithography relies on the precise transfer of patterns onto a wafer. Contaminants left behind by RCA cleaning can cause pattern distortion or line edge roughness (LER), leading to failure in critical dimensions. These imperfections not only degrade the chip’s performance but can also cause overlay errors, making multi-patterning techniques (critical in advanced nodes) more difficult to execute.

2. Etching and deposition:
   The presence of residual contamination can affect deposition and etching steps. For example, metal residues can interfere with the uniformity of thin films during deposition, while surface damage from cleaning may cause etching irregularities. This results in non-uniform layers that can affect device functionality and lead to electrical shorts or breakdowns in the interconnects.

3. Chemical amplification in photoresists:
   The presence of organic residues or metals on the wafer surface can also affect the performance of chemically amplified resists (CARs). Inconsistent photoresist behavior leads to poor pattern transfer, reducing the fidelity of the printed features and further impacting chip performance.

4. Device Reliability:
   Chips with even subtle atomic-level defects are more likely to suffer from electrical leakage or performance degradation over time, leading to reliability issues. This is especially problematic in critical applications, where the longevity of the chip is essential.

How SisuSemi’s solution resolves the issues

SisuSemi’s solution, which leverages low-power, ultra-high-vacuum technology, offers a novel solution to the atomic-level contamination issues caused by RCA cleaning. The key features of the solution are:

1. Ultra-high-vacuum technology for deep cleaning:
   The ultra-high-vacuum (UHV) environment created by SisuSemi's technology enables highly efficient removal of atomic-level contaminants. The solution can remove surface impurities without damaging the wafer or introducing new contamination. This is especially critical after RCA cleaning, where traditional cleaning methods often leave behind trace contaminants that can compromise subsequent processes.

2. Atomic-scale surface precision:
   SisuSemi’s solution ensures that the wafer surface remains pristine by employing non-chemical, atomically precise cleaning methods. This prevents surface damage, ensuring that the wafer is perfectly prepared for the lithography phase. The result is smoother, more uniform surfaces that improve photoresist adhesion, leading to better pattern fidelity and reduced line edge roughness (LER).

3. Improved manufacturing yield:
   By addressing atomic-level defects and contamination, SisuSemi’s solution helps increase manufacturing yield. Wafers that undergo SisuSemi’s UHV cleaning are far less likely to experience defects during subsequent processing stages, reducing the likelihood of functional failures and ensuring more good die per wafer.

4. Reduced chip energy consumption:
   Clean surfaces also contribute to more efficient manufacturing processes. With fewer defects and better material properties, the resulting chips consume less power and exhibit lower leakage currents. This translates to energy savings, particularly in applications like mobile devices, IoT sensors and high-performance computing, where power efficiency is critical.

5. Enhanced chip performance and quality:
   The improved surface cleanliness and defect reduction ensure that the final chips are more reliable, with higher electrical performance and better durability in the field. SisuSemi’s solution also reduces the likelihood of failures due to stress-induced defects, which are common in improperly cleaned surfaces.

Conclusion: The future of semiconductor cleaning

RCA cleaning is an essential step in semiconductor fabrication, but its atomic-level impurities and surface damage can create significant challenges in advanced processes. These defects can cascade through the entire manufacturing chain, affecting lithography, etching, deposition and the final quality of the chip.

SisuSemi’s low-power, ultra-high-vacuum technology offers a powerful solution to these challenges. By addressing the atomic-level impurity issues left by RCA cleaning, SisuSemi ensures that chips are manufactured with higher precision, better performance and greater reliability, all while improving yield and reducing energy consumption.

As the semiconductor industry pushes further into the atomic scale, integrating SisuSemi’s advanced cleaning technology in combination with RCA cleaning will become essential for maintaining the high standards of next-generation chip performance and manufacturing excellence.