slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Microelectronics Processing Physical Vapor Deposition PowerPoint Presentation
Download Presentation
Microelectronics Processing Physical Vapor Deposition

Loading in 2 Seconds...

play fullscreen
1 / 66

Microelectronics Processing Physical Vapor Deposition - PowerPoint PPT Presentation


  • 226 Views
  • Uploaded on

Microelectronics Processing Physical Vapor Deposition. Issues. Vacuum basics Vacuum Technology basics Some vacuum systems Evaporation Sputter deposition Metallization. Vacuum basics. Kinetic theory of gases At relatively low pressures Not too low temperatures

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Microelectronics Processing Physical Vapor Deposition' - khanh


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Microelectronics ProcessingPhysical Vapor Deposition

Microelectronics processing - E. Finkman

issues
Issues
  • Vacuum basics
  • Vacuum Technology basics
  • Some vacuum systems
  • Evaporation
  • Sputter deposition
  • Metallization

Microelectronics processing - E. Finkman

vacuum basics
Vacuum basics
  • Kinetic theory of gases
  • At relatively low pressures
  • Not too low temperatures
  • Molecules described as rigid balls
  • Constant velocity
  • Elastic collisions
  • Redistribution of kinetic energy

Microelectronics processing - E. Finkman

slide4

Vacuum basics

Ideal gas law

PV = nRT (1)

P - pressure

V - volume

T - temperature

n - number of moles

R - gas constant

Microelectronics processing - E. Finkman

slide5

Vacuum basics

Ideal gas law

PV=nRT (1)

P - pressure

V - volume

T - temperature

N - number of moles

R - gas constant

1

R=kBNAV

kB= 1.38x10-23 J/molec K

NAV= 6x1023 molec/mol

Microelectronics processing - E. Finkman

slide6

Vacuum basics

The average molecular speed

vav= (8kBT/M)1/2 (2)

M – molecular weight

The average time between collisions

tav= 1/(21/2 Nd2vav )(3)

d – molecular diameter

N – number density of molecules (per unit volume)

Microelectronics processing - E. Finkman

slide7

Vacuum basics

The average distance between collisions

(the Mean Free Path -  )

 = 1/(21/2Nd2) (4)

Thus, if  is larger than the dimension of

the chamber, the particles will travel

without collisions!

Thus, if  is larger than the dimension of

the chamber, the particles will travel

without collisions!

Microelectronics processing - E. Finkman

slide8

Vacuum basics

In order to increase the

mean free path we have

to reduce N reduce P

Microelectronics processing - E. Finkman

slide9

Vacuum basics

Microelectronics processing - E. Finkman

slide10

Vacuum basics

Microelectronics processing - E. Finkman

slide11

Vacuum basics

Microelectronics processing - E. Finkman

vacuum basics conclusions i
Vacuum basics - Conclusions - I

When the gas flows through a system with

Dimensions V1/3>> , flow is viscous.

When P is lowered,  increases

If  exceeds system dimensions, the

flow becomesmolecular.

Reducing P Molecular flow

No collision between source and target

(less contamination)

Microelectronics processing - E. Finkman

vacuum basics conclusions ii
Vacuum basics - Conclusions - II

Surface and film contamination is determined

by the background pressure of the chamber,

or by the ratio between the partial pressure of

the desired species and that of the

background molecules in the chamber.

Example: what is the value of P for flow through

a tube 5 cm in diameter to be molecular?

Microelectronics processing - E. Finkman

vacuum technology basics
Vacuum Technology basics

S – Pumping speed (volume per unit time, l/sec)

Q – Flow to the pump (mass per unit time, )

Q = PS

The lowest pressure achievable by a given

pump:

P = Q/S

Microelectronics processing - E. Finkman

vacuum technology basics15
Vacuum Technology basics
  • P = Q/S
  • This equation holds when gas is inserted to the chamber
  • A leak:
  • Gas flows intentionally into the chamber
  • Imperfect seal (air leaks in from the outside)
  • Outgasing from chamber walls

Microelectronics processing - E. Finkman

vacuum technology basics16
Vacuum Technology basics

The effect of tubes, orifices, restrictions

are measured in terms of the conductance

C = Q/P P = P1 –P2

Two obstacles in series, C1and C2:

C-1 = C1-1+ C2-1

Tubes, constrictions, valves, and

other components reduce system

conductance.

Microelectronics processing - E. Finkman

typical vacuum system
Typical Vacuum System

1

5

4

2

6

3

Microelectronics processing - E. Finkman

rotary pumps
Rotary pumps

Microelectronics processing - E. Finkman

rotary pump with gas ballast
Rotary pump with gas ballast

Microelectronics processing - E. Finkman

root pump
Root pump

Microelectronics processing - E. Finkman

sorption pumps
Sorption pumps

~800m2/cm3

Microelectronics processing - E. Finkman

high vacuum pumps diffusion pump
High vacuum pumps: Diffusion pump

Gaede 1913

Microelectronics processing - E. Finkman

diffusion pump disadvantage
Diffusion pump disadvantage
  • Diffusion pumps are based on boiling oil.
  • Oil can be transported to the chamber by
  • back-streaming, causing contamination
  • to the processed semiconductor.
  • Partial solutions:
  • Use low vapor pressure oil
  • Insert a cold trap over the pump

Microelectronics processing - E. Finkman

high vacuum pumps cryogenic pump

Cryogenic Pump Turbo Molecular Pump

High vacuum pumps: cryogenic pump
  • High pumping speed
  • High throughput for H2O
  • Momentary power loss is
  • detrimental.
  • Large capacity
  • Need regeneration

Microelectronics processing - E. Finkman

high vacuum pumps turbo molecular pump

Cryogenic Pump Turbo Molecular Pump

High vacuum pumps: turbo-molecular pump
  • High speed rotation
  • blades.
  • Require backing
  • pump.
  • Produces vibration.

Microelectronics processing - E. Finkman

speed versus pressure comparison clarify pump choice

Pumping speed (l/sec)

Pressure (torr)

Speed versus pressure comparison –clarify pump choice

Microelectronics processing - E. Finkman

evaluation of vacuum pumps
Evaluation of vacuum pumps

Microelectronics processing - E. Finkman

measurement of pressure and leak detection

Measurement of Pressureand LeakDetection

Microelectronics processing - E. Finkman

pressure gauges
Pressure Gauges

Microelectronics processing - E. Finkman

mechanical gauges
Mechanical Gauges

Bourdon Gauge

Diaphragm Gauge

Microelectronics processing - E. Finkman

reference point in measuring pressure
Reference point in measuring Pressure

Microelectronics processing - E. Finkman

a mechanical gauge
A mechanical Gauge

Capacitance gauge: the deflection of a membrane

Is measured as a change in capacitance

Microelectronics processing - E. Finkman

thermocouple gauge
Thermocouple Gauge
  • A filament is heated by a constant DC current (20 to 200mA)
  • The filament is exposed to the gas
  • The heat in the filament is transported to the gas
  • As the pressure decreases, the temperature increases
  • We measure the temperature of the filament (by a thermocouple)
  • The pressure is obtained by an output voltage (V<20 mV DC)
  • Pressure range: 2 Torr – 10-3 Torr
  • With an industrial D/A converter, range extended to 103 – 10-3 Torr
  • Pirani sensor: the filament is a thermal resistor

Microelectronics processing - E. Finkman

hot cathode ion gauge
Hot Cathode ion Gauge

Refined by Bayard-Alpert – 1950

Range: 10-2 – 10-10 Torr

Microelectronics processing - E. Finkman

cold cathode vacuum gauge
Cold cathode Vacuum Gauge

Microelectronics processing - E. Finkman

leaks and leak testing

Leaks and leak testing

Microelectronics processing - E. Finkman

places likely to leak
Places likely to leak
  • O-rings seals
  • metal gaskets
  • electrical feedthroughs
  • shut-off valves with through leaks,
  • internal welds/brazes on utility pipes
  • chamber welds

Microelectronics processing - E. Finkman

reasons for poor vacuum
Reasons for poor vacuum
  • high vacuum pump failing
  • high solvent concentration in pump oil
  • poor quality oil in a mechanical pump
  • sample outgassing
  • outgassing from new chamber fixturing
  • increased vapor pressure due to heating
  • venting to air during humid weather
  • helium permeation through rubber or plastic components

Microelectronics processing - E. Finkman

residual gas analysis principle
Residual Gas Analysis - Principle

Mass separation

Quadrupole mass

spectrometer

Microelectronics processing - E. Finkman

residual gas analysis principle40
Residual Gas Analysis - Principle

Lorentz force law F =q(E+vXB(

Newton’s 2nd law F=ma

Mass spectrometry m/q=E+vXB

Microelectronics processing - E. Finkman

physical vapor deposition 1 evaporation
Physical Vapor Deposition:1. Evaporation

Schematic diagram of evaporation equipment

  • Types of evaporation sources:
  • Filament evaporation;
  • Electron beam source.

Microelectronics processing - E. Finkman

evaporation geometry for system using planetary substrate hoder
Evaporation geometry for system using planetary substrate hoder

Microelectronics processing - E. Finkman

slide43

The evaporation rate in g/sec is estimated to be

Where AS the source area in cm 2, m is the gram-molecular mass, T the temperature in K, and Pe the vapor pressure in torr.

Source evaporation rate

Problem alloying!

Microelectronics processing - E. Finkman

evaporation why is not being used in present day si technology

The Contact Hole Filling Problem:

The atoms are coming in straight line from a “point source”, i.e. their incidence on the sample is nearly perpendicular. The hole filling problem looks like this:

The actual situation may look slightly better, due to a small sticking coefficient, which is the ratio of the number of atoms that “stick” on the surface relative to the number of incident atoms:

SC = Freacted/Fincident .

But this effect is usually not so dramatic.

Evaporation – Why is not being used in present day Si technology?

Microelectronics processing - E. Finkman

dc sputter deposition

-V (DC)

(glow discharge)

Cathode shield

Schematic diagram of DC powered sputter deposition equipment

Vacuum

ground

DC Sputter deposition

~-100-1000V

Microelectronics processing - E. Finkman

dc sputter system plasma structure and voltage distribution
DC Sputter systemPlasma structure and voltage distribution

Al, W, Ti, silicides,

other metals

Microelectronics processing - E. Finkman

basic properties of plasma
Basic properties of plasma

Microelectronics processing - E. Finkman

basic properties of plasma48
Basic properties of plasma

Microelectronics processing - E. Finkman

processes in sputter deposition
Processes in sputter deposition

Microelectronics processing - E. Finkman

sputtering yield in a dc system
Sputtering yield in a DC system

Microelectronics processing - E. Finkman

the contact hole filling problem
The contact hole filling problem

Fort aspect ratios A = w/d smaller than approximately 1, the layer at the edge of the contact hole will become unacceptably thin or will even be non-existing - the contact to the underlying structure is not established.

Microelectronics processing - E. Finkman

the contact hole filling problem the real thing
The contact hole filling problem – the real thing

The real thing together with one way to overcome the problem is shown above (the example is from the 4Mbit DRAM generation, around 1988).

Microelectronics processing - E. Finkman

reactive sputter deposition
Reactive sputter deposition

Microelectronics processing - E. Finkman

rf sputter deposition
RF sputter deposition

Microelectronics processing - E. Finkman

rf sputter deposition55

V1/V2 = (A2/A1)m

where A1, and A2 are the respective electrode areas. m was found experimentally to be between 1 and 2.

RF sputter deposition

Microelectronics processing - E. Finkman

magnetron sputter deposition
Magnetron sputter deposition

Microelectronics processing - E. Finkman

deposition methods for thin fims
Deposition methods for thin fims

Microelectronics processing - E. Finkman

comparison of various layer deposition processes
Comparison of various layer deposition processes

Microelectronics processing - E. Finkman

metals can you guess who is the winner

Desired Property

Materials not meeting requirement

Very good conductivity

All but Ag, Cu

High eutectic temperature with Si(> 800 oC would be good)

Au, Pd, Al, Mg

Low diffusivity in Si

Cu, Ni, Li

Low oxidation rate; stable oxide

Refr. Metals, Mg, Fe, Cu, Ag

High melting point

Al, Mg, Cu

Minimal interaction with Si substrate

Pt, Pd, Rh, V, Ni , Mo, Cr (form silicides

easily)

Minimal interaction with poly Si

Same as above

No interaction with SiO2

Hf, Zr, Ti, Ta, Nb, V. Mg, Al

But must stick well to SiO2

?

Must also comply with other substrates,

e.g. TiN

?

Chemical stability, especially in HF

environments

Fe, Co, Ni, Cu, Mg, Al

Easy structuring

Pt, Pd, Ni, Co, Au

Electromigration resistant

Al, Cu

.... and many more,...

Metals – Can you guess who is the winner?

Microelectronics processing - E. Finkman

metalization the winner so far
Metalization – the winner (so far …)

Microelectronics processing - E. Finkman

metallization
Metallization

Microelectronics processing - E. Finkman

metallization62
Metallization

Microelectronics processing - E. Finkman

spiking
Spiking

Microelectronics processing - E. Finkman

electromigration
Electromigration

Microelectronics processing - E. Finkman

deposition processes summary

A series of materials are deposited during processing in thin layers to provide wiring, insulation, and contacts. The main techniques used are physical vapor deposition (PVD) and chemical vapor deposition (CVD). More recently, electro-plating and spin-on processes have been developed for special applications.

  • Schematic cross section of a 2 level IC
  • Oxide patterned using hard mask,
  • Polysilicon gate electrode,
  • PMD,
  • Metal 1,
  • IMD,
  • Metal 2,
  • Passivation layer.
Deposition processes summary

Microelectronics processing - E. Finkman

pvd cluster tool
PVD cluster tool

Microelectronics processing - E. Finkman