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: 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 degrade chip performance and can cause overlay errors, making multi-patterning techniques 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, resulting in non-uniform layers that affect device functionality and lead to electrical shorts or breakdowns.
  3. Chemical amplification in photoresists: Organic residues or metals on the wafer surface can affect chemically amplified resists (CARs). Inconsistent photoresist behavior leads to poor pattern transfer, reducing the fidelity of the printed features and 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, especially in critical applications where chip longevity is essential.

How SisuSemi’s solution resolves the issues

SisuSemi’s solution, which leverages low-power, ultra-high-vacuum technology, offers a novel approach 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 UHV environment enables highly efficient removal of atomic-level contaminants without damaging the wafer or introducing new contamination. This is critical after RCA cleaning, where trace contaminants can compromise subsequent processes.
  2. Atomic-scale surface precision: Non-chemical, atomically precise cleaning ensures the wafer surface remains pristine, preventing surface damage and preparing it perfectly for lithography. This results in smoother surfaces, improved photoresist adhesion, better pattern fidelity, and reduced line edge roughness (LER).
  3. Improved manufacturing yield: By addressing atomic-level defects and contamination, SisuSemi helps increase yield. Wafers cleaned with UHV technology are far less likely to experience defects in subsequent stages, resulting in more good die per wafer.
  4. Reduced chip energy consumption: Clean surfaces improve material properties, leading to lower leakage currents and reduced power consumption. This is particularly beneficial for mobile devices, IoT sensors, and high-performance computing, where energy efficiency is critical.
  5. Enhanced chip performance and quality: The improved surface cleanliness ensures higher electrical performance, better reliability, and reduced likelihood of stress-induced defects common in improperly cleaned wafers.

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 lithography, etching, deposition, and the final chip quality.

SisuSemi’s low-power, ultra-high-vacuum technology provides a powerful solution, addressing atomic-level impurity issues left by RCA cleaning. This ensures chips are manufactured with higher precision, better performance, greater reliability, improved yield, and reduced 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.