Chinese
EnglishBubblers and cylinders for CVD/ALD precursor processing
Chemical vapor deposition (CVD) is a process for depositing solid materials such as nanotubes, nanowires, particles, thin films, etc. onto a substrate by creating reactive species in the gas phase. The reactive species is formed when a precursor gas contacts or passes over a heated substrate. There are several types of CVD, including metal-organic chemical vapor deposition (MOCVD), low-pressure chemical vapor deposition (LPCVD), and atmospheric pressure chemical vapor deposition (APCVD). In the MOCVD process, metal-organic species are used to form thin films of metals and metal compounds such as metal nitrides and metal oxides.
Figure 1. Typical CVD reactor.
A specific form of CVD is the atomic layer deposition (ALD) process, where deposition can be controlled at the atomic level. In this process, various precursors are alternately supplied to the reaction chamber and undergo self-limiting surface reactions, allowing the same amount of material to be deposited in each reaction cycle. This produces very smooth, uniformly thick, alternating layers of high-density material with fewer defects.
Applications of CVD/ALD Processes
CVD/ALD processes are gaining momentum because they can form thin films with high uniformity and conformality, and the thickness can be precisely controlled. The following are applications of CVD processes:
Manufacturing of optical storage media
Production of semiconductor devices
Synthesis of new powder/fiber materials
Production of protective coatings, including high-temperature, corrosion-resistant and wear-resistant coatings
Formation of ceramic composites, optical fibers and dense structural components.
In particular, the ALD process is gaining more and more attention due to its better control over film formation. The following are applications of the ALD process:
Development of electroluminescent device technology
Production of novel high-k gate dielectrics that are expected to be a replacement for silicon dioxide in next-generation metal oxide semiconductor field effect transistors
Manufacturing of microelectronic devices, including thin film capacitors, radiation detectors, switches, ferroelectric memories, integrated circuits, and microelectromechanical structures (MEMS).
The Role of Bubblers and Cylinders in CVD/ALD Processes
While most precursors used in CVD/ALD processes are liquid at room temperature, they are also used in powder form in some cases. Most precursors are sensitive to air and/or water and are very flammable or pyrophoric in nature. Despite this, they exhibit good thermal stability and can be stored for long periods of time if well packaged. For CVD/ALD processes, precursors are usually used directly from the packaging in which they are supplied to avoid handling issues. Therefore, packaging must be considered as an integral part of the product.
Typically, bubblers with internal dip tubes are used as the packaging option for liquids, while stainless steel cylinders with suitable seals and fittings are used for gases. Typically, the transfer of liquid precursors into the reaction chamber is accomplished by bubbling a carrier gas through a container in which the precursor is stored at or below room temperature.
Hydrogen is the most commonly used carrier gas; however, in some cases, nitrogen or other inert gases can also serve this purpose. To avoid condensation of the precursor in the tubing connecting the cylinder to the reaction chamber, the temperature of the cylinder or bubbler should preferably be below room temperature if the vapor pressure of the precursor permits. If cooling is not possible, condensation can be avoided by heating the tubing to above room temperature.
Bubblers and Cylinders from Longyang Biochemical
Longyang Biochemical is a supplier of high-purity specialty chemicals that offers a variety of bubblers and cylinders for CVD/ALD processes.
CVD/ALD Electropolished Stainless Steel Bubblers
Figure 2. Electropolished stainless steel bubbler.
LongYang Bio offers CVD/ALD electropolished stainless steel bubblers with the following features:
Vertical and horizontal configurations
Available in different capacities: 150 ml, 300 ml, 600 ml, 1000 ml, 1200 ml, 2000 ml, 2500 ml and 3000 ml
Choice of in-line valve or valve rotated 90 degrees from the fill port
Available with or without dip tube and in various lengths
Can be equipped with diaphragm sealed valves
Can be equipped with valves specifically for high temperature operation (315°C).
CVD/ALD Stainless Steel Cylinders
Figure 3. Stainless steel standard components.
Figure 4. Stainless steel cylinder.