Steps involved in chip fabrication are1. All the devices on the wafer are made at

the same time.2. After the circuitry has been placed on the

chip, the chip is overglassed to protect it. Only those areas which connect to the outside world will be left uncovered.

3. The wafer finally passes through a test station. Test probes send test signal patterns to the chip and monitor the output of the chip.

4. The yield of a process is the percentage of die which pass this testing.

5. The wafer is then scribed and separated up into individual chips. These are then packaged.

6. Chips are ‘binned’ according to their performance.

1. CMOS Technology- First proposed in 1960s but was not seriously considered until the severe limitations in power density and dissipation occurred in NMOS circuits.- Now this is the most dominant technology in IC manufacturing. It employs both PMOS and NMOS transistors to form logic elements.-Advantage : It’s logic elements draw significant current only during the transition from one state to another. Hence power is conserved.

PULL DOWN

PULL UPOUTPUT

INPUT

VDD

OUTPUTINPUT

A

B

Z

VDD

2. BiCMOS

A known deficiency of MOS technology is its limited load

driving capabilities. Bipolar transistors have higher gain,

better noise characteristics and better high frequency

characteristics. These gates can be an efficient way of

speeding up VLSI circuits. CMOS fabrication process can be

extended for BiCMOS. This transistor consist of three

regions-source, gate and drain. If the source and drain

regions are doped with N-type material and substrate with P-

type then it is called as N-channel MOSFET. If the source and

drain regions are doped with P-type material and substrate

with N-type then it is called as P-channel MOSFET.

Polysilicon GateSiO2

Insulator

n+ n+

p substrate

channel

Source Drain

n transistor

G

S

D

SB

LW

G

S

D

substrate connectedto GND

p+ p+

n substrate

channel

Source Drain

p transistor

G

S

D

SB

Polysilicon GateSiO2

Insulator L

W

G

substrate connectedto VDD

- Wafer Processing- Photolithography- Oxide Growth & Removal- Material Deposition & Removal- Diffusion of Impurities- Putting it all together

- Start with crucible of molten silicon (≈1425oC)

- Insert crystal seed in melt

- Slowly rotate / raise seed to form single crystal boule

- After cooling, slice boule into wafers & polish

Crucible

MoltenSilicon

Current production: 200mm (10”)

Newest technology: 300mm (12”)

Die - Single IC chip300mm wafer

Image Source: Intel Corporation

- All dice on wafer processed simultaneously

- Each mask has one image for each die- The basic approach:

- Add & selectively remove materials Metal - wires Polysilicon - gates Oxide - insulation

Selectively diffuse impurities

Photolithography is the key

- Coat wafer with photoresist (PR)

- Shine UV light through mask to selectively expose PR

- Use acid to dissolve exposed PR

- Now use exposed areas for- Selective doping- Selective removal of

material under exposed PR

Wafer

Photoresist

Mask

UV Light

- Thin Oxide- Add using chemical deposition-Used to form gate insulator & block active

areas

- Field Oxide (FOX) - formed by oxidation- Wet (H20 at 900oC - 1000oC) or Dry (O2 at

1200oC)- Used to insulate non-active areas

Silicon Wafer Silicon Wafer

SiN / SiO2

FOX FOXSiO2 Thin Oxide

- Introduce dopant via epitaxy or ion implant e.g. Arsenic (N), Boron (P)

- Allow dopants to diffuse at high temperature

- Block diffusion in selective areas using oxide or PR

- Diffusion spreads both vertically, horizontally

Silicon

Diffusion

Blocking Material (Oxide)

- Need to accommodate both N, P transistors

-Must implement in separate regions - wells (tubs) N-well P-well

-Alternate approach: Silicon on Insulator (SOI)

n-wellp substrate

n well

n substrate

p well

p-welln tub p tub insulator

n epi p epi

twin-tub SOI

- Overall chip doped as p substrate, tied to GND

- Selected well areas doped n, tied to VDD

n+ n+

p substrate

channelp+ p+

n well

channel

Gnd

n+ n+

p substrate

channelp+ p+

n well

channel

VDD

P substrate

- Substrate- Well- Active

Areas- Gates- Diffusion- Insulator- Contacts- Metal

wafer

n well

1. Mask Design using Layout Editor- user specifies layout objects on different layers- output: layout file

2. Pattern Generator- Reads layout file- Generates enlarged master image of each mask

layer- Image printed on glass reticle

3. Step & repeat camera- Reduces & copies reticle image onto mask- One copy for each die on wafer- Note importance of mask alignment

1. The dielectric constant of SiO2 is 3.9. This gives rise to a large coupling capacitance between wires which has to be minimized. The solution is to use low-k dielectrics and the proposed materials should have approx K=3

2. Another problem arises due to small electric field under transistor gates which has to be maximized. The solution is to use high-k dielectrics and the proposed materials would have K>>4 .

- Most photolithography is done using UV with 248nm wavelength. But if the wavelength is less than the value, it gives rise to interference problems.

- The solution to this are: 1. Optical proximity correction (OPC) 2. Phase-shifting masks 3. Other light sources: 193nmUV, Extreme UV, X-Rays, E-beam lithography.

- Normal mask - light spreads & overlaps- Phase shifting mask - cancels overlap- Drawback: requires 2 masks per litho. step

(Expensive)

Graphic source: Numerical Technologies

Optical switches are generally used as :-a. HDMI (High Definition Multimedia Interface)

It is an audio video interface that is use to transmit both digital audio and video streams of data which are uncompressed and encrypted. For instance, many consumer electronics such as high definition flat panel TVs, DVD disc players, Set Top Boxes, AV receivers and Camcorders, etc now offer the option of HDMI connections for a true digital experience.

b. Nano-optical switches- restores sightThis helps in developing the treatments for eye diseases such as the loss of light detectors in the retina which is the major cause of blindness. So some nano-photoswitches are put in the cells of the retina for ‘restoring light sensitivity’ in people with degenerative blindness.

IBM Extends Industry Leading Custom Chip Technology to Embedded Devices

IBM has announced two new 65 nanometer Application-Specific Integrated Circuit (ASIC) product offerings, including the company's first ever comprehensive low power ASIC offering for the fast growing wireless, mobile and consumer electronics market. An ASIC is an integrated circuit customized for a particular use, rather than intended for general-purpose use. Usually, a chip designed solely to run in a cell phone is an example of an ASIC.

UEGO control circuit board portion with ASIC:- A method and apparatus for controlling Universal Exhaust Gas Oxygen (UEGO) sensors comprises an application specific integrated circuit (ASIC) that includes a sensor control utilizing proportional-integral-derivative control loop, sensor drivers for generating pumping currents that reflect the changes of voltages representative of oxygen levels in the reference and test chambers of the UEGO sensor, a communication circuit for communicating with an engine control module, and output buffers for conditioning replications of the pumping current for delivery to an output circuit.

A TV graphics demonstration system is a multimedia application based on PC, intended for home entertainment. The main functions of the system are graphics superimposing and screen capture. The system is implemented and verified by the PC-added video and graphics evaluating board.

FPGA, DSP, ASIC growth is driven by demand for flexibility in Medical Imaging Equipment. Medical imaging equipment demands various processing requirements based on the specific data acquisition principles and algorithms used in image processing. the advantages of FPGA in digital signal processing over other processors and custom IC [integrated circuit] make it a viable alternative for most equipment, including current generation PET [positron emission tomography] machines and volume imaging conducted in CT [CAT scan] that requires high performance computing.