AN900 Datasheet, PDF (2/15 Pages) STMicroelectronics – INTRODUCTION TO SEMICONDUCTOR TECHNOLOGY

INTRODUCTION TO SEMICONDUCTOR TECHNOLOGY
1 THE FABRICATION OF A SEMICONDUCTOR DEVICE
The manufacturing phase of an integrated circuit can be divided into two steps. The first,
wafer fabrication, is the extremely sophisticated and intricate process of manufacturing the
silicon chip. The second, assembly, is the highly precise and automated process of pack-
aging the die. Those two phases are commonly known as “Front-End” and “Back-End”. They
include two test steps: wafer probing and final test.
Figure 1. Manufacturing Flow Chart of an Integrated Circuit
"Front-End"
WAFER
FABRICATION
Wafer
Probing
"Back-End"
ASSEMBLY
Final
Test
VR02103A
1.1 WAFER FABRICATION (FRONT-END)
Identical integrated circuits, called die, are made on each wafer in a multi-step process. Each
step adds a new layer to the wafer or modifies the existing one. These layers form the ele-
ments of the individual electronic circuits.
The main steps for the fabrication of a die are summarized in the following table. Some of
them are repeated several times at different stages of the process. The order given here
doesn't reflect the real order of fabrication process.
PhotoMasking
Etching
Diffusion
Ionic
Implantation
Metal
Deposition
This step shapes the different components. The principle is quite simple (see draw-
ing on next page). Resin is put down on the wafer which is then exposed to light
through a specific mask. The lighten part of the resin softens and is rinsed off with
solvents (developing step).
This operation removes a thin film material. There are two different methods: wet
(using a liquid or soluble compound) or dry (using a gaseous compound like oxygen
or chlorine).
This step is used to introduce dopants inside the material or to grow a thin oxide
layer onto the wafer. Wafers are inserted into a high temperature furnace (up to
1200 ° C) and doping gazes penetrate the silicon or react with it to grow a silicon
oxide layer.
It allows to introduce a dopant at a given depth into the material using a high energy
electron beam.
It allows the realization of electrical connections between the different cells of the
integrated circuit and the outside. Two different methods are used to deposit the
metal: evaporation or sputtering.
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