Friday, October 02, 2009

Basic fabrication steps in VLSI

The basic fabrication steps in VLSI are:
1.oxidation
2.photolithography and etching
3.diffussion and implantation
4.mettallization
1. oxidation
The oxidation process is one of the most important processes in VLSI fabrication. The development of high quality silicon dioxide has helped to establish the dominance of si in the production of commercial ICs. generally Sio2 functions as an insulator in a number of device structures or as a barrier to diffussion or implantation during device fabrication.
There are two types of Sio2 growth methods:
1. dry oxidation
2.wet oxidation
dry oxidation is generally used to form thin oxides in a device structures because of its si-sio2 interface characteristics. It is implemented in processes such as the gate dielectric growth, the quality of which is extremely important for the scaling and performance of today's integrated circuit technology. An oxidation concentration versus oxidation layer thickness figure is plotted almost instantaneously after the users specify the necessary parameters and conditions. The slope of the curve depicts the oxidation flux. The oxidation process is simulated after one click on the web interface, while all the complicated details and equation-solving procedures are hidden behind the scene. The interactive interface of the module and its simplicity of usage demonstrates the module's educational value in that it helps students and engineers build intuition into the oxidation process with minimum learning curve. Insightful comparison, such as one between thin and thick oxide growth, can be done easily. Moreover, the module can be used as a handy and efficient "oxidation flux calculator".

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