Miniaturização

Question 1

Vantagens do Multi-Core

Answer 1

• Potência: Parallel signal processing is an efficient method of achieving high performance. Several “cores” offer high performance per area for parallel
  operations, when compared with a single core
• Design: The behavior of a smaller and simpler core is much easier to predict using the conventional design tools. Reduced complexity makes it easier to
  design and to produce.
• Tolerância a defeitos: “Smaller cores represent a cheap way of improving the yield. Redundant cores can be used and those with defects can be deactivated.

Question 2

Advantages da miniaturização

Answer 2

• Mais transistores
• Menor tensão de trabalho

Causam:
- Better functionality
- Better performance
- Cost reduction
- Lower power consumption

Question 3

Miniaturization

Answer 3

• Scale down
  -Constant electric field
  -Constant voltage
  -Quasi Constant Voltage
  -General scaling law

Question 4

Strained Silicon

Answer 4

– Growing silicon on a silicon-germanium alloy crystal
– Silicon atoms are farthest apart from each other which reduces the electrostatic forces to which charge carriers are subjected when crossing the crystalline structure
– Deformation in the lattice parameter in the order of 1% may increase the mobility of electrons in 70%

Question 5

Propriedades Silicon-germaniun alloys

Answer 5

Germanio
* Diamond like structure
* Face centered cubic
* Covalent bonding

Alloys Si1-xGex
* Gap and resistivty decreases with the Ge
content

Question 6

Strained silicon nos mosfets

Answer 6

P-MOSFET
* Mobility is improved when the semiconductor channel (Si or SiGe) is deformed by perpendicular compression or biaxial tension parallel to interface

N-MOSFET
* Mobility is improved when the semiconductor channel (Si or SiGe) is deformed by parallel tension or perpendicular compression

Question 7

High- K dieletrics

Answer 7

– High dielectric constant
– Thermodynamic stability in contact with the silicon
– Formation of good quality interfaces (epitaxial growth or amorphous structures)
– Favorable band misalignment (reduced leakage current at the gate by carrier injection in the dielectric bands

Question 8

High dielectric constant

Answer 8

High k materials have lower band gap than SiO2

Question 9

Thermodynamic stability

Answer 9

-It is important to avoid reaction with silicon
-Decomposition in metallic phase or formation of silicides / silicates.
-It is required that the dielectric layer has a higher heat of formation than SiO2.
- Formation of interfacial layers decreases the effective dielectric capacitance

Question 10

High-k dielectrics
* Structure and interfaces

Answer 10

– Stabilization of an amorphous structure up to high temperatures can be achieved by mixing two oxides for the gate dielectric

– Amorphous or crystalline structures are preferred (not polycrystalline). Grain
boundaries can act as preferred centers for leakage current appearance or
dopant diffusion.

-– Interface with high-κ dielectrics have at least an order of magnitude more
defects when compared with Si/SiO2
interface

– The high-κ dielectrics themselves have a higher internal defect density since
they are deposited and not thermally grown

Question 11

High-k dielectrics
* Band misalignment

Answer 11

– A good insulator has at least 1 eV difference at the band gap to prevent the injection of carriers from the semiconductor

Question 12

Conceitos

Answer 12

Multilayer:
-aumento da densidade de IC’s
-Usado em memorias

Question 13

Short channel effects

Answer 13

As the technology scaling reaches channel lengths deeper into sub-micron dimensions, second order effects, that were ignored in devices with long channel length, became very important.

Question 15

Short channel effects: MOSFET‘s

Answer 15

• In small transistors, source/drain depletion regions extend into the channel
• Impacts the amount of charge required to invert the channel
• And thus makes VT a function of channel length (and VD)

– The main second order effects are:
* Velocity Saturation
* Threshold Voltage Variations
* Hot Carrier Effects

Question 16

Short Channel Effects
* Channel length modulation

Answer 16

So far the lateral extension of the depletion layer into the channel (ΔL) has been ignored. Not anymore: for short channel devices, ΔL reduces the effective channel length and it is VD dependent.