Optimized etching processes and well-tuned parameters allow Creative Biolabs to provide high-precision low-roughness etching services with well-defined shapes to our clients all over the world.
Etching
Etching is a critical step after the conversion of the standardized pattern on the photomask to photoresist. The advanced microfabrication technology platform allows us to provide easy-to-implement wet etching and dry etching capable of complex structures. Wet etching uses a chemical that is highly corrosive to the substrate material and inert to the resist layer to directly corrode the substrate surface. Dry etching uses particles in the gas or plasma phase to erode the substrate.
Photoresist
Before etching, the substrate surface is coated with a layer of photoresist to act as a resist to protect the substrate material from unplanned damage. In the case of positive photoresists, specific wavelengths of light destroy their internal chemical composition, inducing the molecules into a more soluble form. With negative-tone resists, light induces the polymer to form covalent bonds so that it does not dissolve in subsequent processing. In general, positive resists have better photo solubility contrast than negative resists, but have poorer adhesion to the substrate material (usually silicon) and are more susceptible to chemical corrode.
Fig 1. Workflow of etching. (Creative Biolabs)
Isotropic etching is the simplest, most common and most practical wet etching method. Isotropic etching proceeds equally in three spatial directions and produces spherical-like cavity structures. The channel widens significantly after etching and produces a fillet at the bottom of the channel with a radius roughly equal to the channel depth. The channel width (Wc) has a direct relationship to the channel depth (Dc) and the photomask width (Wm). Isotropic etching only reacts to specific materials, so it does not harm the underlying film during the patterning of multiple layers of materials. At present, silicon dioxide and metal aluminum are mostly processed by isotropic etching.
Fig 2. Schematic of isotropic etching. (Creative Biolabs)
Anisotropic etching is a common technique in processing single-crystal silicon, which can produce channels with flat surfaces along a specific crystallographic orientation. Erosion rate and planar extension direction are determined by the crystallographic orientation followed by the chemical corrode.
Dry etching is a pattern transfer technique widely used in silicon nitride, polysilicon, metal and alloy materials. Dry etching uses the interaction of plasma and the material to be etched to remove the substrate material not protected by the photoresist film. Dry etching is divided into sputter etching, chemical etching, and physical/chemical etching with inhibitor/no inhibitor. Dry etching can achieve isotropic or anisotropic etching, and the direction of plane extension is controlled by system instead of following the crystal structure.
Our Services
The optimization of the micromachining platform has provided extraordinary improvements to various etching techniques related to the fabrication of microfluidic systems. Abundant manufacturing experience and experimental data allow Creative Biolabs to control the geometry of etched objects within microns. Our experienced standard etching technology allows us to process high-precision, smooth-surfaced microchannels on a variety of substrate materials, and provide you with patterned pure silicon molds, photoresist molds, metal molds, glass/silicon chips or PDMS chips. With our help, you may effectively advance research on disease diagnosis and bioassay at a reasonable cost, so don't hesitate to contact us for more information.
For Research Use Only. Not For Clinical Use.
