Fabrication of Transistors in 3D IC Technology:

There are total six fabrication steps for the MOSFET :

1)Oxidation : Growing of Lear’s silicon dioxide on the surface of silicon wafer.

2) Diffusion : Impurity atoms into the bulk of silicon from higher to lower concentration.

3) Ion implantation: It used for the process to make microchips.

4) Deposition: Various metals are deposited on silicon buffer.

5) Etching : Selectively removing a layer of material.

6)Photolithography : process to transfer pattern to a layer on chip.

MOSFET Transistor Fabrication Steps in 3D IC:

As shown in above diagram,

- In first part there is photoresist and prepared silicon wafer, and mechanism for the projected lights.

- In the second part ,there is projected mechanism and have mask, lens and patterns are projected repeatedly onto the wafer.

- In the third part, its basically exposed photoresist is removed in this process.

-In fourth part, areas unprotected by photoresist are etched by gases so the shape get as shown in fig.

· In fifth part there is pine showers the etched area and doping them so it is doped region. So new photoresist is spun on buffer and step two to four is repeated.

- In sixth part similar cycle is repeated to layer down metal links but the transistor, and also have metal connectors and the fabricated transistor. So this was the all about MOSFET transistor fabrication steps.

- Positively doped silicon buffer is first coated with an insulting layer of silicon dioxide , shown in yellow color and this is done in chemical vapors deposition.

- An ultraviolet light sensitive thin layer of photoresist in blue color is applied to the silicon dioxide surface and evenly spread across the wafer.

- The first mask is placed over the wafer and ultraviolet light is projected on to the mask areas of photoresist exposed to light and those shielded remain soft.

- Unexposed photoresist is removed by washing with a solvent , leaving the hardened resist and underlying the silicon dioxide layer

-Upper layer of the silicon dioxide is removed by etching with hot gasses .

- The hardened photoresist is removed with chemical solvent leaving an on even silicon dioxide over entire wafer.