In this blog post, we will provide an easy-to-understand overview of the basic principles and components of CVD, its major variations, and its industrial applications.
Background
When I first heard the news of Shuji Nakamura winning the Nobel Prize in 2014, I wondered whether the development of the blue LED was truly an achievement worthy of the Nobel Prize. After reviewing Shuji’s papers and presentation materials at the time, I discovered that a somewhat unfamiliar process called two-flow MOCVD had significantly contributed to the award. This experience sparked my interest in CVD (Chemical Vapor Deposition) technology and motivated me to summarize its structure, principles, various forms, and application areas.
Principles and Components of CVD
MOCVD is a branch of CVD, and to understand it, one must first grasp the difference between CVD and PVD. PVD (Physical Vapor Deposition) is a method that physically deposits material onto a substrate by evaporating it with heat or using high-energy particles; sputtering is a representative example. In contrast, CVD is a method that chemically forms thin films on a substrate by decomposing raw material gases using heat or light, or by inducing oxidation or reduction reactions. In other words, the name derives from the fact that the raw materials for the thin film are “deposited” onto a solid surface through chemical reactions in the gaseous state.
CVD equipment typically consists of four components: the gas inlet, the exhaust port, the substrate holder, and the power supply. The gas inlet supplies raw materials to the reaction chamber, while the exhaust port discharges gases or byproducts generated after the reaction. The substrate holder secures the substrate and controls its movement, while the power supply unit provides the energy required for the reaction. Substrate fixation is achieved through vacuum suction, clamps, or electromagnetic forces, and heaters are used for temperature control; in some cases, plasma is generated to utilize the substrate as an electrode.
Various Forms of CVD
Since the requirements for thin-film fabrication via deposition vary significantly depending on the application, CVD has evolved into several variants tailored to specific purposes. This section introduces three representative types: LPCVD, PECVD, and MOCVD.
The first is Low-Pressure CVD (LPCVD). In the semiconductor industry, LPCVD is widely used to deposit insulating films such as SiO₂ and Si₃N₄, as well as heat-resistant thin films like tungsten, molybdenum, and tantalum, using substrates that can withstand high temperatures, such as silicon wafers. Since materials that require significant energy for interatomic bonding must be deposited stably at high temperatures, LPCVD typically operates at temperatures above 600°C, where the feed gas decomposes and deposits onto the substrate. This method yields dense thin films with excellent electrical properties and offers advantages in terms of productivity by allowing multiple substrates to be processed simultaneously.
The second method is Plasma-Enhanced CVD (PECVD). With the advancement of display technology, particularly the demand for flexible and wearable displays, there has been a growing need to deposit thin films onto glass or plastic substrates at low temperatures. PECVD ionizes gas using plasma, enabling the deposition of semiconductor and dielectric thin films even at low temperatures, making it suitable for display manufacturing. Changes in the composition and bonding state of the plasma-generating feedstock and the gas used for film formation have a significant impact on the properties of the thin film.
The third method is Metal Organic CVD (MOCVD). MOCVD is a core technology for manufacturing advanced devices such as LEDs, lasers, and solar cells. It uses organometallic compounds (in gaseous or liquid form) as feedstock to grow thin films through pyrolysis or thermochemical reactions. The use of organometallic precursors allows reactants to be deposited more readily onto the substrate surface, enabling efficient layered growth of semiconductors and the deposition of insulating and metallic thin films. In particular, process optimizations such as two-flow MOCVD have contributed to achievements like the development of blue LEDs.
Conclusion
The development of high-tech industries can be summarized as “speed” and “precision,” and these two factors are particularly emphasized in the semiconductor industry. Since smaller and more numerous devices must be precisely arranged on limited substrate space, various forms of CVD technology have played a pivotal role. By appropriately selecting and developing CVD processes—such as LPCVD, PECVD, and MOCVD—tailored to specific purposes, significant efficiency gains have been achieved in productivity and property control. Moving forward, thin-film deposition technology will continue to play a central role at the forefront of advanced industries.
