Alpha 801 D

The Tokyo Electron Alpha 801 D is a thermal diffusion furnace used in semiconductor manufacturing for processes such as oxidation, annealing, and chemical vapor deposition. Diffusion furnaces heat wafers to controlled high temperatures in a tubular reaction chamber, allowing gases to react with or diffuse into the silicon surface.

The Alpha 801 D operates as a vertical diffusion furnace, where wafers are loaded into a quartz boat that is slowly inserted into a heated vertical tube from below. The tube is surrounded by multi-zone resistive heaters that maintain a uniform temperature profile across the wafer load. Process gases are introduced at the top of the tube and flow downward over the wafers, enabling precise control of gas composition and reaction kinetics.

A typical process cycle consists of loading wafers into the furnace at a low temperature, ramping to the target temperature under controlled atmosphere, holding at temperature for the desired reaction time, and then cooling down before unloading. The system includes pyrometry or thermocouple-based temperature sensing and a vacuum/purge gas handling manifold to prevent contamination and adjust ambient conditions.

Thermal diffusion furnaces like the Alpha 801 D are used in front-end-of-line (FEOL) and middle-of-line (MOL) processing steps. Common applications include gate oxide growth, source/drain drive-in anneals, interlayer dielectric deposition via low-pressure chemical vapor deposition (LPCVD), and poly-Si deposition.

The Alpha 801 D can be used for thermal oxidation of silicon to form silicon dioxide layers, for doping silicon with boron, phosphorus, or arsenic via diffusion from solid or gaseous sources, and for annealing implants to activate dopants and repair crystal damage.

Additional applications include the deposition of silicon nitride and polysilicon films by LPCVD, as well as low-temperature oxidation (LTO) processes. The furnace is suitable for both batch processing of multiple wafers per run and for integrated process sequences that require tight thermal budgets.