Applications of Silicon Components: LPCVD and Thermal Processing

Silicon Components for Furnace Tubes (Heat Treatment, LPCVD )

Low-Pressure Chemical Vapor Deposition (LPCVD) equipment refers to devices where process gases undergo chemical reactions on the substrate surface at high temperatures (350-1000℃) and low pressure (10-1000mTorr), depositing reaction products on the substrate surface to form thin films. LPCVD equipment’s reaction chamber mainly consists of a furnace tube. By placing wafers inside the furnace tube and heating them, the environment reaches the conditions necessary for the process gases to react chemically, achieving thin film coating. Heat treatment refers to manufacturing processes conducted at high temperatures, also requiring furnace tubes as reaction 

chambers. In the semiconductor field, heat treatment primarily includes processes like thermal oxidation, diffusion, and annealing. For instance, in dry oxygen oxidation, oxygen is introduced into a high-temperature furnace tube, reacting with silicon to form a silicon oxide film. High-temperature diffusion doping involves heating to make dopants diffuse from high-concentration regions to low-concentration regions, thus achieving doping. During the ion implantation process, the ion beam knocks silicon atoms out of the lattice structure, damaging the silicon wafer, which needs high-temperature annealing to get the displaced silicon atoms back into the lattice points and repair the damage. The chamber structures and silicon components used in heat treatment and LPCVD equipment are as follows:

Image Source: DSTC Prospectus

Traditional furnace tube components are commonly made of quartz and silicon carbide. Quartz can only be used in environments up to 950℃ (risk of warping at1000℃); silicon carbide can be used at higher temperatures but has long delivery times and high prices. The thermal expansion rates of silicon carbide and quartz differ significantly from silicon wafers, readily causing friction with wafer backs and resulting in defects like scratches. Silicon carbide and quartz components have certain limitations, whereas silicon-made components can effectively resolve these issues. Silicon components can maintain high strength and ultra-high purity in high-temperature environments, preventing chip damage and contamination. Additionally, silicon components have the same thermal expansion coefficient as silicon wafers, reducing the risk of friction and improving yield rates. In the future, silicon components are expected to be widely used in furnace tube equipment. The performance comparison among silicon, quartz, and silicon carbide components is as follows:

Silicon components used in heat treatment equipment and LPCVD equipment are listed below:

Silicon Boat		In heat treatment and LPCVD process equipment, the silicon-wafer-cassette is an important part for carrying wafers in the furnace tube.
Tiled Boat		Used to support silicon wafers in a horizontal furnace
Silicon Boat Base		Used to support the silicon boat in heat treatment and LPCVD equipment, and to provide insulation and thermal insulation
Silicon Jet Tube		Used as an injection/airway for silane and silicon nitride gases in the LPCVD process
Silicon Inner Tube		Installed on the outer side of the silicon boat, it plays a role in gathering gases such as silane and silicon nitride in the LPCVD equipment; Plays a role in insulation, uniform heating, and blocking metal impurities in heat treatment equipment