CVD Process and Epitaxial Growth

What is the primary goal of stacking wafers vertically during chemical vapor deposition?

To increase the throughput of the process

What is the direction of gas flow in the reactor?

x-direction

What is the effect of the boundary layer on the mass transfer coefficient?

It decreases the mass transfer coefficient

What is the purpose of using gas injectors along the tube in chemical vapor deposition?

To compensate for the depletion of source gas Signup and view all the answers

What is the desired flow regime in chemical vapor deposition?

Laminar flow Signup and view all the answers

What is the assumption made in the CVD growth rate model?

Mass transport proceeds by diffusion Signup and view all the answers

What is the effect of reducing pressure from 1 atmosphere to 1 Torr on hG?

hG increases by ~100 times Signup and view all the answers

What is the primary advantage of operating in a reaction limited regime in LPCVD?

Higher sensitivity to temperature Signup and view all the answers

Why is a 5-25°C temperature gradient often created in LPCVD?

To offset source gas depletion effects Signup and view all the answers

What is the effect of low pressure on auto-doping in LPCVD?

Decreases auto-doping due to faster removal of out-diffused dopant gas Signup and view all the answers

What is the typical operating pressure range for LPCVD reactors?

0.25-2.0 Torr Signup and view all the answers

In which mode can PECVD avoid charge buildup for insulators?

RF plasma mode Signup and view all the answers

Why can wafers be stacked vertically in LPCVD reactors?

Because transport of reactants is not rate-limiting Signup and view all the answers

What is a limiting factor of the reaction rate in a CVD process?

Surface chemical reaction rate Signup and view all the answers

What is the typical process temperature range for PECVD?

100 - 400°C Signup and view all the answers

What type of CVD is commonly used for epitaxial growth of III-V compounds for optoelectronic devices?

MOCVD Signup and view all the answers

What is the main difference between PECVD and sputter deposition?

PECVD has more collision in the gas phase and less ion bombardment on the substrate Signup and view all the answers

What is the sequence of steps involved in a CVD process?

Transport of reactants to the deposition region, transport of reactants through the boundary layer, adsorption of reactants, surface chemical reaction Signup and view all the answers

What is the condition for out-diffusion to occur in CVD film growth?

Film thickness = vt > Dt Signup and view all the answers

What is the main drawback of Atmospheric Pressure Chemical Vapor Deposition (APCVD)?

All of the above Signup and view all the answers

What is the advantage of operating at low pressure in Chemical Vapor Deposition (CVD)?

Increased percentage of reactant gases in the carrier gas Signup and view all the answers

What is the relationship between the gas diffusion coefficient (DG) and the total pressure (Ptotal) in the mass transfer limited regime?

DG is inversely proportional to Ptotal Signup and view all the answers

What is the reason for the low throughput of APCVD?

Only a small percentage of the gas is reactant gases Signup and view all the answers

What is the configuration required for APCVD at high temperature?

Horizontal configuration Signup and view all the answers

What is a consequence of shadowing in directional diffusion to the surface?

Deterioration of the step coverage and filling Signup and view all the answers