A two-step surface cleaning technology for removing high electron affinity contaminants from semiconductor and 2D materials

Background

The field of semiconductor manufacturing, particularly at advanced technology nodes and in the synthesis of two-dimensional (2D) materials like transition metal dichalcogenides (TMDs), demands extremely clean surfaces to ensure optimal device performance. As device dimensions shrink below 10 nanometers and new materials are integrated, even trace levels of surface contaminants can significantly degrade electronic properties, reliability, and yield. Processes such as etching and deposition, which are fundamental to device fabrication, often leave behind adsorbate contaminants—especially halogens and excess chalcogen atoms—that are difficult to remove without damaging the delicate underlying structures. The need for highly selective, non-destructive cleaning methods has become increasingly critical as the industry pushes the limits of miniaturization and material complexity.

Current approaches to removing these contaminants, particularly in TMD synthesis, typically rely on hydrogen-based chemistries to eliminate excess chalcogen atoms. However, these methods suffer from several drawbacks: hydrogen doses must be precisely controlled to avoid stripping essential chalcogen atoms from the TMD lattice or reducing the material to its metallic form, which can irreversibly alter its properties. Additionally, hydrogen can itself become a contaminant, diffusing into the material and altering its electronic and magnetic characteristics. For halogen removal, conventional cleaning techniques often lack the selectivity or gentleness required, risking substrate damage or incomplete contaminant removal. These limitations highlight the urgent need for a self-limiting, universal, and damage-free cleaning method that can effectively address both chalcogen and halogen contaminants without compromising the integrity of advanced semiconductor and 2D material surfaces.

Technology

This technology provides a highly effective, two-step surface cleaning solution for semiconductor and 2D material fabrication, particularly targeting the removal of high electron affinity adsorbate contaminants such as halogens. The process begins with the selective etching of excess chalcogen atoms from the surface using remotely generated halogen atoms (e.g., fluorine, chlorine, bromine, or iodine) derived from halogen-containing gases. This approach avoids the use of hydrogen, which can be difficult to control and potentially damaging to sensitive materials like transition metal dichalcogenides (TMDs). Following this, a post-cleaning step employs low-energy electrons (below 3 eV), generated by a direct plasma or electron beam, to remove any residual halogen adsorbates. These electrons attach to the surface-bound halogen atoms, causing them to desorb as negative ions via a dissociative electron attachment (DEA) mechanism. The process is self-limiting and operates at substrate-compatible temperatures, making it suitable for a wide range of materials, including advanced silicon, III-V semiconductors, and 2D TMDs.

What sets this technology apart is its universal, damage-free, and self-limiting nature. Unlike conventional hydrogen-based cleaning, which risks altering or damaging the underlying material, this method leverages the high electron affinity of halogen adsorbates to ensure selective removal without disturbing the substrate or device layers. The use of remotely generated halogen atoms prevents plasma-induced damage during the etching step, while the low-energy electron cleaning step is precisely tuned to avoid breaking substrate bonds. This dual-action approach is applicable to a broad spectrum of materials and device architectures, enabling the integration of TMDs and other advanced materials into next-generation microelectronics with pristine, contaminant-free surfaces. The technology’s adaptability, effectiveness, and compatibility with existing fabrication processes make it a significant advancement for semiconductor manufacturing at the nanoscale.

Benefits

• Selective removal of excess chalcogen atoms without damaging the underlying 2D material or semiconductor substrate.
• Effective elimination of residual halogen adsorbates via low-energy electron-induced dissociative electron attachment (DEA), ensuring clean surfaces.
• Self-limiting and damage-free cleaning process suitable for delicate materials like transition metal dichalcogenides (TMDs) and advanced sub-10 nm semiconductor technologies.
• Use of remotely generated halogen atoms avoids plasma-induced damage during etching.
• Universal applicability across a wide range of materials including metals, semiconductors, insulators, and 2D materials such as WS2 and MoS2.
• Improves device performance by preventing contamination-related degradation of electrical and magnetic properties.
• Compatible with existing microelectronic fabrication processes and supports integration of novel 2D materials.

Applications

• Advanced semiconductor device fabrication
• 2D material integration for electronics
• Atomic layer deposition surface cleaning
• Sub-10 nm node manufacturing
• III-V compound semiconductor processing

Additional info

This two-step method cleans semiconductor and 2D material surfaces. First, remote halogen atoms etch excess chalcogen contaminants. Second, low-energy electrons (below 3 eV) remove residual halogen adsorbates via dissociative electron attachment. This self-limiting, damage-free process prevents substrate damage, crucial for advanced microelectronic fabrication by ensuring contaminant-free surfaces.