Ethylene (C ₂ H ₄) is not directly used as a core process gas in semiconductor manufacturing, but its derivatives or related processes play an important role in specific processes. The following is a detailed analysis of the application and advantages of ethylene in semiconductor manufacturing:
1. The main applications of ethylene in semiconductor manufacturing
(1) Precursors in Chemical Vapor Deposition (CVD)
Carbon based thin film deposition: Ethylene can be used as a carbon source to prepare thin films such as silicon carbide (SiC) and diamond-like carbon (DLC) in CVD or plasma enhanced chemical vapor deposition (PECVD). These films are used for hard masks, passivation layers, or anti reflective coatings.
Graphene growth: In high-temperature CVD systems, ethylene reacts with metal catalysts (such as copper foil) to generate graphene, which is used for flexible electronics, high-frequency transistors, or sensors.
(2) Auxiliary gases in etching process
Selective etching: In plasma etching, ethylene can be mixed with hydrogen gas (H ₂) to form hydrocarbon polymers to protect the sidewalls and improve the anisotropy of etching (such as the "passivation" step in silicon etching).
(3) Epitaxial growth
Silicon carbide (SiC) epitaxy: Ethylene is used as a carbon source to grow SiC epitaxial layers together with silane (SiH ₄), which is used for power semiconductor devices (such as high-voltage devices in electric vehicles).
(4) Electron beam photoresist with photoresist assisted process: Vinyl compounds (such as polyvinyl alcohol cinnamate) were used in early photoresists, but their derivatives are more commonly used in modern processes.
2. Advantages of Ethylene
(1) High reactivity
The carbon carbon double bond of ethylene is prone to breakage and can efficiently participate in reactions in plasma or high temperature environments, making it suitable for rapid deposition or etching processes.
(2) Carbon purity control
As a simple hydrocarbon, ethylene can precisely control the doping concentration of carbon (such as in SiC), avoiding the introduction of impurities.
(3) Process compatibility
Compatible with commonly used gases in semiconductor fabs, such as SiH ₄ and NH3, it is easy to integrate into existing CVD or etching equipment.
(4) Cost effectiveness
Ethylene industrial production is mature, cost-effective, and suitable for large-scale manufacturing.
3. Comparison with other gases
Compared to methane (CH ₄): Ethylene provides a higher carbon deposition rate in CVD, but may require higher temperature activation.
Compared to acetylene (C ₂ H ₂): Ethylene is more stable and less prone to producing unnecessary carbon particles (soot), making it suitable for high uniformity processes.
4. Challenges and limitations
Toxicity and safety: Ethylene is flammable and explosive (explosion limit 2.7%~36%), and strict control of storage and transportation is required.
By product control: Hydrogen or carbon polymers may be generated in plasma processes, and process parameters need to be optimized.
5. Future development direction
Advanced packaging: Ethylene derivatives may be used for the deposition of low - κ dielectric materials (such as porous carbon doped oxides).
Wide bandgap semiconductors: The demand for vinyl precursors in SiC and GaN devices may grow with the power electronics market.
summarize
Ethylene mainly serves key processes such as thin film deposition, etching, and epitaxial growth in semiconductor manufacturing through its high reactivity and carbon source characteristics. Its advantages lie in low cost, high purity, and strong process compatibility. Although safety risks need to be taken into account, it is irreplaceable in specific applications such as SiC power devices. With the diversification of semiconductor materials, the application of ethylene and its derivatives may further expand.