EE4645 Microfabrication Engineering: Czochralski Method and Crystal Growth
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Questions and Answers

What is the unit of the latent heat of fusion (L) for silicon in the CZ growth method?

cal/gm

How does the concentration of the dopant in the grown crystal depend on the material used as the dopant?

It depends on both the material used as the dopant and its concentration.

What is the physical significance of the Stefan-Boltzmann constant (σ) in the equation for maximum pull rate in CZ growth?

It relates to the radiative heat transfer process.

What is the role of the thermocouple in the CZ growth method?

<p>It is used to control the temperature of the melt.</p> Signup and view all the answers

What is the unit of the thermal conductivity (kM) for silicon in the CZ growth method?

<p>cal/(sec.cm.K)</p> Signup and view all the answers

How does the maximum pull rate (vpmax) in CZ growth depend on the crystal diameter?

<p>It is inversely proportional to the square root of the crystal diameter.</p> Signup and view all the answers

What is the significance of Heinrich Hertz's demonstration in 1887 in the context of semiconductor development?

<p>His demonstration of radio waves paved the way for the development of wireless systems and eventually contributed to the advancements in semiconductor technology.</p> Signup and view all the answers

What is the main purpose of Resistivity Profiling measurement in semiconductor characterization?

<p>To determine the resistivity of a semiconductor material as a function of depth or position.</p> Signup and view all the answers

What is the significance of Deep Level Transient Spectroscopy (DLTS) in defect analysis of semiconductors?

<p>DLTS is a technique used to analyze deep-level defects in semiconductors, which is essential for understanding the electrical properties of semiconductor materials.</p> Signup and view all the answers

What is the primary application of Scanning Tunneling Microscopy (STM) in semiconductor characterization?

<p>To visualize the surface morphology of semiconductor materials at the atomic level.</p> Signup and view all the answers

What is the significance of C-V measurement in dopant profiling of semiconductors?

<p>C-V measurement is used to determine the doping profile of semiconductor materials, which is essential for understanding the electrical properties of semiconductor devices.</p> Signup and view all the answers

What is the relationship between the pull speed and the grown crystal diameter in the Czochralski (CZ) method?

<p>The maximum pull rate for the crystal growth is inversely proportional to the square root of the grown crystal radius.</p> Signup and view all the answers

What is the heat balance equation that describes the heat transfer processes in the CZ growth method?

<p>Heat balance equation: L + kL<em>A1</em>dT/dx1 = kS<em>A2</em>dT/dx2</p> Signup and view all the answers

What is the Stefan-Boltzmann law equation that describes the heat radiation from the crystal?

<p>dQ = (2πrdx)(σεT^4)</p> Signup and view all the answers

What is the expression for the crystal growth rate in the CZ method?

<p>dm/dt = v_p*NA</p> Signup and view all the answers

What is the thermal conductivity variation with temperature in the CZ growth method?

<p>kS = kM*T</p> Signup and view all the answers

What is the maximum pull rate equation derived from the heat balance and heat transfer equations?

<p>v_p max = LN / (2σεkM*T_M^(5/2) r^(1/2))</p> Signup and view all the answers

Study Notes

Czochralski (CZ) Growth Method

  • CZ growth method is used to grow single crystal silicon ingots.
  • The method involves dipping a seed crystal into a crucible containing molten silicon and slowly pulling it up while rotating it.

Modeling the CZ Growth

  • The crystal growth rate is given by: dm = v_p * N * A * dt, where v_p is the pull speed, N is the density of the crystal, A is the cross-sectional area of the crystal, and dt is the time.
  • The heat balance equation is: L * dm/dt + k_L * dT/dx1 = k_S * dT/dx2, where L is the latent heat of fusion, k_L is the thermal conductivity of the liquid, k_S is the thermal conductivity of the crystal, and dT/dx1 and dT/dx2 are the thermal gradients at the isotherms.
  • The maximum pull rate is given by: v_p max = √(L * N / (2 * σ * ε * k_M * T_M^5)) / (3 * r), where σ is the Stefan-Boltzmann constant, ε is the emissivity, k_M is the thermal conductivity at the melting point, T_M is the melting point, and r is the radius of the crystal.

Example Problem

  • Calculate the maximum pull rate for growing a 6” diameter Si crystal ingot using the CZ growth method.
  • Given values: L = 430 cal/g, N = 2.328 g/cm³, k_M = 0.048 cal/(sec.cm.K), σ = 0.55, T_M = 1690 K, and ε = 0.55.
  • Solution: v_p max = 23.6 cm/hr = 0.38 cm/min.

Doping of CZ Crystal

  • Dopants are added to the melt in the form of heavily doped silicon prior to growth.
  • The concentration of the dopant in the grown crystal depends on both the material used as the dopant and its concentration.
  • Examples of dopants used: As, P, and B.

Semiconductor Characterizations

Resistivity Measurement

  • Methods: Four Point Probe Measurement, Resistivity Profiling, and Contact Resistance Measurement.

C-V Measurement for Dopant Profiling

Defects in Semiconductors

  • Types of defects: Shallow Level Impurities, Deep Level Impurities, and Deep Level Transient Spectroscopy (DLTS).

Microscopy

  • Types of microscopy: Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM), and Electron Beam Based Microscopy.

History of IC

  • 1865: James C. Maxwell predicted the existence of radio waves.
  • 1887: Heinrich Hertz demonstrated the radio waves.
  • 1895: Marconi built a wireless system capable of transmitting signals at 2.4 km.
  • 1901: Great improvements in Telephone Herald in Budapest, Hungary.

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Description

Test your understanding of the Czochralski method, a process used to grow single-crystal silicon ingots. This quiz covers the modeling of CZ growth, heat balance, and the relationship between pull speed and crystal diameter.

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