Plasma Treatment to Create a Hydrophilic Surface on Silicon Substrates

TEMPE, Ariz. - PrZen -- Recent testing: initial contact angles of 45 degrees to 75 degrees were measured.  After plasma treatment in our AutoGlow 1000 the contact angle was measured < 2 degrees. Testing performed in the AutoGlow 1000 production plasma cleaner.

Plasma Treatment is used to modify silicon wafer surface properties, specifically targeting hydrophilicity. This process involves exposing the silicon substrate to a low-pressure plasma environment, typically utilizing gases such as oxygen or argon/hydrogen mixture. Through the interaction between plasma species and the silicon surface, a cascade of intricate chemical reactions occurs, leading to the formation of hydrophilic functional groups, primarily hydroxyl (-OH) moieties, on the surface.

The plasma-induced surface modification proceeds through sequential steps. Initially, energetic plasma species, including ions, electrons, and radicals, impact the silicon surface, breaking surface bonds--forming reactive species like silicon radicals and dangling bonds. Subsequently, these species react with surrounding gas molecules, predominantly oxygen or hydrogen, resulting in the incorporation of oxygen or hydrogen atoms onto the silicon surface.

The introduction of these functional groups, notably hydroxyl (-OH) groups, alters the silicon wafer's surface chemistry, rendering it hydrophilic. Hydroxyl groups exhibit a strong affinity for water molecules due to their polar nature, facilitating water adsorption and enhancing surface wetting. This transition, from hydrophobic to hydrophilic surfaces, holds significant importance in various technological domains, notably microfluidics, where precise control over surface wettability is vital for fluid manipulation and bioanalytical applications.  Also important for bonding applications.

In semiconductor manufacturing, plasma treatment is particularly relevant for enhancing adhesion between silicon surfaces and functional layers like dielectric films or photoresists, thereby improving device performance and reliability. Moreover, the ability to tailor surface properties at the nanoscale level enables the fabrication of advanced nanostructures and surface patterns, paving the way for the development of innovative electronic and photonic devices.

Plasma treatment emerges as a sophisticated methodology, offering unparalleled precision in tailoring silicon wafer surfaces. Our test show results to increase the hydrophilic surfaces to reducing contact angles.  Plasma treatment plays a pivotal role in various applications such as increasing bonding strength.

Testing was performed on the AutoGlow 1000 plasma system configured for RIE and Direct Plasma.