The process flow for fabrication the resister ic
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1. The Process flow for fabrication the resister IC. Step I: The Beginning-Choosing a substrate Before actual wafer fabrication, we must choose the starting wafers. The major choices are the type (N or P), resistivity, and orientation.

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The Process flow for fabrication the resister IC

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The process flow for fabrication the resister ic

1

The Process flow for fabrication the resister IC

Step I: The Beginning-Choosing a substrate

Before actual wafer fabrication, we must choose the starting wafers. The

major choices are the type (N or P), resistivity, and orientation.

In most IC circuits, the substrate has a resistivity in the range of 25-

50cm, which corresponds to a doping level on the order of 1015cm-3.

The other major parameter we need to specify in the starting substrate is

the crystal orientation. Virtually all modern silicon integrated circuits are manufactured today from wafer with a (100) surface orientation. The principal reason for this is that the properties of Si/Sio2 interface are significantly better when a (100) crystal is used.

Lecture # 2


Cmos process flow

CMOS Process Flow


The process flow for fabrication the resister ic

Cross section of the final CMOS integrated circuit.


The process flow for fabrication the resister ic

3SiH4+4NH3Si3N4+12H2

Silicon nitride form a barrier against the impurities moving toward the

Si surface.


Photolithography

4

Photolithography

  • In order to transfer resister information from the design to the wafer, a process known as photolithography is used.

  • For this process a material known as photoresist is first spread on the wafer. It is usually baked at about 100oC in order to drive off

  • solvants from the layer (photolithographic process will be covered in chapter 5 through.

Lecture # 2


The process flow for fabrication the resister ic

Open windows for thick oxidation


The process flow for fabrication the resister ic

Bird’s beak


The process flow for fabrication the resister ic

P Well Formation

1016 -1017 cm-3


The process flow for fabrication the resister ic

N Well Formation


The process flow for fabrication the resister ic

High temperature Drive-In

2-3 micron


The process flow for fabrication the resister ic

NMOS gate formation and adjusting VTH

The single most important parameter in the both NMOS

and PMOS devices is the threshold voltage

To adjust VTH , two terms that are important are the

doping concentration and the oxide capacitance.


The process flow for fabrication the resister ic

PMOS Gate Formation


The process flow for fabrication the resister ic

Regrown of gate oxide

Why oxide layer is stripped and then regrown?


The process flow for fabrication the resister ic

Deposition of polysilicon layer

SiH4 Si+2H2

Low ploy sheet resistivity and low gate resistance is required.


The process flow for fabrication the resister ic

Selective Etching: to locate MOS gates

Selectivity and anisotropy are big deal hare


The process flow for fabrication the resister ic

Tip or extension (LDD) formation


The process flow for fabrication the resister ic

Tip or extension (LDD) formation


The process flow for fabrication the resister ic

Sidewall Spacer fabrication


The process flow for fabrication the resister ic

Aniostropic Etching


The process flow for fabrication the resister ic

Formation of NMOS source and Drain region


The process flow for fabrication the resister ic

Formation of PMOS source and Drain region


The process flow for fabrication the resister ic

High temperature Drive-In

TED is a big issue hare!


The process flow for fabrication the resister ic

Contact and local Interconnect formation


The process flow for fabrication the resister ic

TiSi2


The process flow for fabrication the resister ic

Multilevel metal formation


Basic nmos process flowchart

8

Basic NMOS process flowchart.

Lecture # 2


Basic bipolar process flowchart

9

Basic bipolar process flowchart.

Lecture # 2


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