CVD Process and Epitaxial Growth
29 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

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

  • To decrease the velocity of the gas flow
  • To decrease the thickness of the boundary layer
  • To increase the temperature of the reaction
  • To increase the throughput of the process (correct)

    • What is the direction of gas flow in the reactor?

  • Along the susceptor
  • x-direction (correct)
  • Across the stagnant layer
  • y-direction

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

  • It decreases the mass transfer coefficient (correct)
  • It increases the mass transfer coefficient
  • It has no effect on the mass transfer coefficient
  • It depends on the temperature of the reaction

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

    <p>To compensate for the depletion of source gas</p> Signup and view all the answers

    What is the desired flow regime in chemical vapor deposition?

    <p>Laminar flow</p> Signup and view all the answers

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

    <p>Mass transport proceeds by diffusion</p> Signup and view all the answers

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

    <p>hG increases by ~100 times</p> Signup and view all the answers

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

    <p>Higher sensitivity to temperature</p> Signup and view all the answers

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

    <p>To offset source gas depletion effects</p> Signup and view all the answers

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

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

    What is the typical operating pressure range for LPCVD reactors?

    <p>0.25-2.0 Torr</p> Signup and view all the answers

    In which mode can PECVD avoid charge buildup for insulators?

    <p>RF plasma mode</p> Signup and view all the answers

    Why can wafers be stacked vertically in LPCVD reactors?

    <p>Because transport of reactants is not rate-limiting</p> Signup and view all the answers

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

    <p>Surface chemical reaction rate</p> Signup and view all the answers

    What is the typical process temperature range for PECVD?

    <p>100 - 400°C</p> Signup and view all the answers

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

    <p>MOCVD</p> Signup and view all the answers

    What is the main difference between PECVD and sputter deposition?

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

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

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

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

    <p>Film thickness = vt &gt; Dt</p> Signup and view all the answers

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

    <p>All of the above</p> Signup and view all the answers

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

    <p>Increased percentage of reactant gases in the carrier gas</p> 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?

    <p>DG is inversely proportional to Ptotal</p> Signup and view all the answers

    What is the reason for the low throughput of APCVD?

    <p>Only a small percentage of the gas is reactant gases</p> Signup and view all the answers

    What is the configuration required for APCVD at high temperature?

    <p>Horizontal configuration</p> Signup and view all the answers

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

    <p>Deterioration of the step coverage and filling</p> Signup and view all the answers

    What is a drawback of cold wall reactors compared to hot wall reactors?

    <p>Worse gas convection</p> Signup and view all the answers

    What is the primary mechanism of energy transfer in PECVD?

    <p>Radio-frequency induced plasma</p> Signup and view all the answers

    What is the typical frequency used in PECVD?

    <p>13.56 MHz</p> Signup and view all the answers

    What is the primary benefit of the energy supplied by the plasma in PECVD?

    <p>Enhanced film density and composition</p> Signup and view all the answers

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser