Silicon-based Microfluidic Chip Fabrication Service

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Introduction Techniques of Silicon Chip Fabrication Features

Creative Biolabs offers an extensive range of silicon chip fabrication services to assist you in the intricate development of various patterns and structures on silicon. We employ advanced technologies to develop bespoke microstructures that align with your requirements.

Introduction

Silicon was the first material used in microfluidics, but it was soon supplanted by glass and polymers. Silicon has many advantages, such as resistance to organic solvents, ease of metal deposition, high thermal conductivity, and stable electroosmotic mobility. The surface chemistry of silicon is characterized by silanol groups (−Si−OH), allowing for chemical modification of the silicon surface. This modification can help reduce nonspecific adsorption and enhance cell growth, among other applications.

Fig. 1 The microfluidic chip fabricated by silicon etching process. Fig. 1 The microfluidic device fabricated by the two-step silicon etching process.¹

Techniques of Silicon Chip Fabrication

Photolithography

Photolithography is a process that combines optical principles and chemical etching to create tiny microfluidic channel patterns on silicon wafers. The process begins by coating the surface of the silicon wafer with a layer of photosensitive material known as photoresist. Next, the photoresist is exposed to ultraviolet light through a specific mask. This exposure causes chemical changes in the photoresist, allowing the exposed areas to be etched away using a chemical solution. As a result, the desired pattern is preserved on the silicon wafer.

The pattern is created using photolithography, followed by selective chemical processing to modify the properties of the silicon substrate or to define the geometry of an overlying film deposited on the substrate. Silicon dioxide (SiO₂) and silicon nitride (Si₃N₄) are commonly used as "sacrificial" materials, which are later removed, while polycrystalline silicon (poly-Si) is utilized to form structural layers.

Fig. 2 Schematic illustration of the microfabrication process. Fig. 2 The microfabrication process.¹

Wet Etching

Wet etching is a crucial process in the manufacturing of compound semiconductor devices. This technique relies on the chemical reaction between the etching solution and the material being immersed in it, resulting in soluble products that facilitate the removal of the desired area. Wet etching has the advantages of low cost and large-scale production. However, it features inherent isotropy in the etching process, which leads to undercutting beneath the mask, making it unsuitable for patterns smaller than 2 microns.

Dry Etching

A. Reactive Ion Etching (RIE):

Fig. 3 The silicon wafer made by Creative Biolabs. (Creative Biolabs Original) Fig. 3 The silicon wafer fabricated by Creative Biolabs.

Reactive Ion Etching (RIE) is a widely used etching technology in micro-nano processing due to its high etching rate, excellent anisotropy, and large-area uniformity. RIE removes deposited materials on a wafer by chemically reactive plasma to create a pattern. This plasma is generated by an electromagnetic field at low pressure (in a vacuum). The high-energy ions in the plasma then attack and react with the surface of the wafer.

B. Deep reaction ion etching (DRIE)

Deep reactive ion etching (DRIE) is a specific type of reactive ion etching (RIE). It allows a highly anisotropic etching process to create deep, steep holes and trenches in wafers, usually with high aspect ratios.

Features

The depth that can be manufactured on silicon wafers is 2~500um.
Able to meet aspect ratio 1:1~10:1.
Stable manufacturing accuracy in the micron range.
Excellent electrical and thermal conductivity.

Creative Biolabs provides an extensive range of silicon chip fabrication services. Whether you require custom configurations or standardized patterns, our dedicated team is here to support you every step of the way, ensuring that your project meets the highest standards of performance and reliability. Please contact us for more details.

Reference

Chen, Xi, et al. "Study on Functionality and Surface Modification of a Stair-Step Liquid-Triggered Valve for On-Chip Flow Control." Micromachines 11.7 (2020): 690. Distributed under Open Access license CC BY 4.0, without modification.

For Research Use Only. Not For Clinical Use.