Chapter 5, Dielectric and Polysilicon Film Deposition Video Solutions, Ulsi Technology

Problem 1

In order to increase the capacitance of MOS capacitors in ULSI DRAMs, $\mathrm{Ta}_2 \mathrm{O}_5$ has been plasma-deposited to replace the oxide/nitride/oxide dielectric. The dielectric constants of $\mathrm{SiO}_2$, nitride, and $\mathrm{Ta}_2 \mathrm{O}_5$ are about $3.9,7.6$, and 25 , respectively. What is the capacitance ratio for the capacitors with the $\mathrm{Ta}_2 \mathrm{O}_5$ and oxide/nitride/oxide dielectrics for the same dielectric thickness, provided that the oxide/nitride/oxide has thickness ratio $1: 1$ for the oxide to the nitride?

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18:47

Problem 2

For the CVD of phosphosilicate glass, $20 \%$ silane is mixed in $80 \%$ nitrogen at a reaction temperature of $500^{\circ} \mathrm{C}$. The flow rate is 600 sccm (standard cubic centimeter per minute). The reactor is loaded with 10 wafers, 10 cm in diameter. The growth rate and film density are $600 \AA / \mathrm{min}$ and $2 \times 10^{22} / \mathrm{cm}^3$, respectively. With what efficiency is the silane transformed into silicon dioxide film? (Hint: A flow of one sccm is defined as a flux of one $\mathrm{cm}^3$ of gas, as measured at 273 K and 760 torr, per minute.)

Niamat Khuda

Numerade Educator

03:47

Problem 3

Phosphosilicate glass consists of $\mathrm{SiO}_2$ and $\mathrm{P}_2 \mathrm{O}_5$. Derive the relationships of weight percent (wt \%), atom percent (at\%), and mole percent (mole \%), for the dopant concentration.

Shahina -

Numerade Educator

01:15

Problem 4

(a) What factors will affect the step coverage of the deposited oxide films?
(b) What techniques have been used to improve the step coverage of the deposited oxide films?

Andreas Papavassiliou

Numerade Educator

Problem 5

The LOCOS process often causes a "bird's beak" phenomenon, i.e., field-oxide encroachment under the silicon nitride mask. A decrease of the stress between CVD nitride and Si substrate can reduce this effect. What methods can you suggest to attain this purpose?

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Problem 6

If LPCVD polysilicon deposition has an activation energy of 1.65 eV and a deposition rate of $8 \mathrm{~nm} / \mathrm{min}$ at $600^{\circ} \mathrm{C}$, what is the deposition rate at $620^{\circ} \mathrm{C}$ ?

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03:30

Problem 7

In a PECVD system, the chamber pressure is 1 torr, the total gas flow rate is 100 sccm , the temperature is $27^{\circ} \mathrm{C}$, and the volume of the chamber is $1000 \mathrm{~cm}^3$. What is the average residence time for a gas molecule in the PECVD reactor?

Mukesh Devi

Numerade Educator

03:28

Problem 8

For an ECR CVD system the magnetic field is 875 gauss. What is the frequency of the microwave power to generate electron cyclotron resonance?

Donya Dobbin

Numerade Educator