Diamond Like Carbon

Diamond-Like Carbon (DLC) is a form of amorphous carbon (a-C) that contains a mixture of sp² (graphite-like) and sp³ (diamond-like) carbon bonds. It is not crystalline diamond, but it has many of diamond’s desirable properties, such as:

• High hardness (can approach diamond levels, depending on sp³ content)

• Chemical inertness (resistant to oxidation, corrosion, and chemical attack)

• Low friction and wear resistance

• High electrical resistivity (can be insulating or semiconducting depending on hydrogen content and doping)

• Wide optical transparency (in the infrared to visible range, depending on deposition method)

Because of these properties, DLC is widely used in protective coatings, optics, biomedical devices, and increasingly in semiconductor fabrication.

How DLC is Fabricated

DLC films are typically deposited as thin coatings (from a few nanometers to several microns thick) using plasma-based processes, such as:

• Plasma-Enhanced Chemical Vapor Deposition (PECVD): Common method using hydrocarbon gases (CH₄, C₂H₂, etc.) in plasma.

• Sputtering: Carbon target sputtered in argon plasma.

• Ion Beam Deposition: Direct carbon ion implantation for high sp³ bonding fraction.

• Cathodic Arc Evaporation: Produces dense, hard DLC films.

Hydrogenated DLC (a-C:H) is most common in microelectronics, as hydrogen helps reduce defects and stress in the film.

Uses of DLC in Semiconductor Fabrication

In semiconductor and micro/nanofabrication, DLC is valuable because it combines chemical resistance, mechanical durability, and tunable electrical properties:

1. Etch Mask / Hardmask

   • DLC is used as an etch mask during plasma etching (e.g., for SiO₂, Si₃N₄, or metals).

   • Its high resistance to fluorine- and chlorine-based plasmas makes it superior to photoresists in some processes.

   • Useful in dual damascene and advanced interconnect processes.

2. Low-k / Dielectric Layer

   • Modified DLC (fluorinated DLC or doped DLC) can serve as an interlayer dielectric because of its relatively low dielectric constant compared to SiO₂.

   • Can reduce RC delay in interconnects.

3. Diffusion Barrier

   • Acts as a barrier to metal diffusion (e.g., Cu into Si or dielectrics).

   • Protects underlying layers from oxidation and contamination.

4. Passivation / Protective Coatings

   • Provides chemical and mechanical protection for MEMS devices and sensors.

   • Used as an anti-stiction layer in NEMS/MEMS.

   • Serves as an encapsulation layer for devices exposed to harsh environments.

5. Masking Layer for Ion Implantation

   • DLC films can withstand high doses of ion implantation without deformation, making them useful as masks for selective doping.

6. Photomask and Lithography Applications

   • In EUV lithography research, DLC has been investigated as an absorber material due to its stability and absorption properties.

✅ Summary:
Diamond-Like Carbon (DLC) is an amorphous carbon film with diamond-like mechanical, chemical, and optical properties. In semiconductor fabrication, it is mainly used as an etch hardmask, diffusion barrier, low-k dielectric, and passivation layer. Its strength lies in its hardness, chemical inertness, and tunable electrical properties, making it increasingly important for advanced nodes, MEMS/NEMS, and protective layers in microelectronics.