INTEGRATED CIRCUITS

Introduction Brief history Scale of integration Types of IC’s Wafer fabrication process IC’s fabrication techniques Advantages Disadvantages Applications Conclusion References

Contents

Integrated circuits

1940’S – Initial stage.

1945’s – Bell labs established a group to develop a semiconductor replacement for vacuum tubes.

1947’s – Transistor invented.

1951’s – Junction transistors invented.

1958’s – Integrated circuits invented.

Brief History

Small scale integration (SSI)

Medium scale integration (MSI)

Large scale integration (LSI)

Very large scale integration (VLSI)

Ultra large scale integration (ULSI)

Scale of integration

Wafer scale integration (WSI)

System on a chip (SOC)

3D IC’s

Analog IC’s

Digital IC’s

Mixed signal IC’s

Types of IC’s

Silicon shaping: Removal of ends Surface grinding Grounding of flats Slicing of ingots Lapping Edge contouring Chemical etching Polishing Chemical cleaning

Wafer preparation

Silicon is a hard & brittle material.

Industrial grade diamond is the most suitable

material for shaping & cutting silicon.

Silicon shaping:

Remove seeds and tang ends.

Metallurgical grade silicon (MGS).

Cutting is done using a circular saw.

Removal of ends:

Rotating diamond grinding tool.

X-ray diffraction techniques.

Surface grinding:

Primary flats

Secondary flats

Grounding of flats:

Inner diameter sawing

Diamond saw

Slicing of ingots:

The wafer flatness produced at this step is

better than 2 micro meter.

Mixture of AL2O3 & glycerin.

Lapping:

Diamond tool.

Prevents defects.

Helps in smooth deposition of photoresist.

Edge contouring:

Acid etching:• acid bath• etchant Alkali etching: mixture of NaOH:H2O or KOH:H2O

Chemical etching:

For smooth surface

Batch wafer process

Single wafer process

Slurry

Polishing:

Silicon wafers are cleaned chemically to remove organic films, heavy metals

Aqueous solution of NH4OH-H2O2, HCL-H2O2.

Chemical cleaning:

Diffusion and ion implantation Oxidation and film deposition Epitaxial growth Lithography Etching Photo resist Deposition

IC fabrication techniques:

Diffusion & ion implantation

Oxides are grown or deposited on the surface of the wafer

Film deposition: thermal oxides dielectric layers polycrystalline oxides metal films

Oxidation & film deposition

The growth of ultra pure layer of crystalline silicon.

Approx 3% of silicon wafer.

Contaminate free for the subsequent construction of transistor.

Epitaxial growth

lithography, Deposition, Etching & photo resist

Small size

Low weight

Easy replacement

High speed

High temperature tolerance

Advantages

Lack of flexibility

High power requirements

Disadvantages

Automobiles

Appliances

computers

Applications

Modern computing, communication, manufacturing and transport system including the internet, all depends on the existence of integrated circuits.

Conclusion