Re: I am eager to know how micro chips store a lot of information?

Area: Computer Science Message ID Number: 1168659119.Cs

Question:

I have a lot of interest in micro chips and I wanted to design one so I
would like to know I can do so?

yours sincerely

harindarmohan

Greetings Harindarmohan:

References:

1. Wikipedia: Integrated Circuits

http://en.wikipedi a.org/wiki/Integrated_circuits

2. Wikipedia: Binary Number System

http://en.wikipe dia.org/wiki/Binary_numeral_system

3. Semiconductor Lithography The Basic Process

nih http://www.lith oguru.com/scientist/lithobasics.html

Background:
The technical name for a microchip is an integrated circuit (IC) . An IC is an electronic circuit that is reduced to
microscopic dimensions to about a one millimeter square. The circuit contains thousands of transistors, diodes, wires
and other electronic components each about one micrometer (40 micro inches) or less in size. Most ICs are fabricated
on wafers of single crystal silicon (Si), which is known as a semiconductor material because the flow of electricity
through layers on the surface of the crystal can be electronically controlled. A typical experimental wafer of Si is
about 15 cm (6 inches) in diameter and one millimeter (400 micro inches) thick. In manufacturing, wafers as large as
a 76 centimeters (30 inches) in diameter are often used. Thus an experimental wafer could contain about 170 of identical
one centimeter square electronic circuits on it’s surface while a manufacturing wafer could contain as many as 7,000
identical circuits.

There are many steps in making an IC. First the electronic circuit is designed on several large sheets of special drawing
paper by a circuit designer. This is called the art work.

The design on the art works are then reduced in size by a factor of about 10,000 and printed on a Si wafer in a device
called photolithographic mask.

The ICs are then chemically processed in layers by depositing material through the mask and by removing material to create a three
dimensional circuit on the surface of the wafer. The growing of material on the wafer is called deposition and is
accomplished by several different machines. The removal of material is called etching and is often, but not always,
accomplished with acid.

A few of the circuits across the wafer are electrically tested to determine if the wafer was correctly processed.

The wafer is then sliced into individual circuits in a process called dicing.

Each chip is then placed in a holder with external wire contacts or pins and wires for power and signal input and signal
output are attached to the chip in a process called packaging.

The IC fabrication process is described in great detail in Reference 3.

The type of IC you are asking about is a memory IC. This type of circuit is shown in Reference 1. Typically each binary
bit of information in a memory IC requires at least one transistor, which can change it’s out put from 0 to +1 volt or
+1 to 0 volts. Each of these circuits can be very complex and can store as many as 100 million bits of information in
binary form as voltages switch between 1 and 0. Thus each electronic circuit will need at least 100 million transistors
plus the control circuits that store the bits or read out the bits of information see Reference 2). The layout of a
memory IC is also shown in Reference 1.

Answer:
The circuit designer that you ask about begins the IC design process by laying out the basic circuit that they want to
fabricate on a set of master drawings each about one meter square (the art work). Each mask drawing can contain many
thousands of electronic devices, including transistors and often takes weeks or months to draw. Because many of the
portions in the final circuit are identical, a mask can be used over and over in a process called a step and repeat across
the surface of a Si wafer. However the masks must be photographically reduced in size from about one square meter in size
to one square centimeter in size, a reduction in size by a factor of 10,000. As many as a dozen masks might be required,
one for each layer that is built up on the chip or removed from the chip. The masks then form a complex three dimensional
electronic circuits on the surface of the Si wafer as shown in Reference 1.

Many universities now have IC circuit design classes were students prepare art work designs and their designs are then fabricated
in commercial IC fabrication facilities. The IC companies cooperate with the universities because there is a great demand
for people with the skills required to design IC circuits.

Thank you for your interesting question.

Best regards, Your Mad Scientist
Adrian Popa