22-12-2012, 04:29 PM
Silicon Wafer Processing
1Silicon Wafer.pdf (Size: 1.41 MB / Downloads: 40)
Introduction
The processing of Silicon wafers to produce integrated circuits involves a good deal of chemistry and
physics. In order to alter the surface conditions and properties, it is necessary to use both inert and toxic
chemicals, specific and unusual conditions, and to manipulate those conditions with both plasma-state
elements and with RF (Radio Frequency) energies. Starting with thin, round wafers of silicon crystal, in
diameters of 150, 200, and 300mm, the processes described here build up a succession of layers of
materials and geometries to produce thousands of electronic devices at tiny sizes, which together
function as integrated circuits (ICs). The devices which now occupy the surface of a one-inch square IC
would have occupied the better part of a medium-sized room 20 years ago, when all these devices
(transistors, resistors, capacitors, and so on) were only available as discreet units.
The conditions under which these processes can work to successfully transform the silicon into ICs
require an absolute absence of contaminants. Thus, the process chambers normally operate under
vacuum, with elemental, molecular, and other particulate contaminants rigorously controlled. In order to
understand these processes, then, we will begin the study of semiconductor processing with an overview
of vacuum systems and theory, of gas systems and theory, as applied specifically to these tools, and of
clean room processes and procedures
The semiconductor industry reflects and serves an extraordinary revolution in both materials science and
in data processing and storage. As recently as 1980, most individuals had no idea that computers would
ever impact their personal lives. Today, many families own one or two computers, and use many other
computers and dedicated processor systems in their appliances and automobiles. The intrusion of
electronics and computer technology into our lives and the devices we use daily is growing at an
exponential rate, and Moore’s Law still applied in the computer world. This is one of the few markets in
which, as time passes, the power and capacity of the products grows steadily, while the cost of that
power and capacity drops.
Thickness Sorting
Following slicing, silicon wafers are often sorted on an automated basis into
batches of uniform thickness to increase productivity in the next process step,
lapping. During thickness sorting, the wafer manufacturer can also identify defect
trends resulting from the slicing process.
Lapping & Etching Processes
Lapping removes the surface silicon which has been cracked or otherwise damaged
by the slicing process, and assures a flat surface. Wafers are then etched in a
chemically active reagent to remove any crystal damage remaining from the
previous process step.
Thickness Sorting and Flatness Checking
Following lapping or etching, silicon wafers are measured for flatness to identify and control defect
trends resulting from the lapping and etching processes. Wafers are also often sorted on an automated
basis according to thickness in order to increase productivity in the next process step, polishing.
Process Steps Details
In this sterile environment, the wafers are exposed to a multiple-step photolithography process that is
repeated once for each mask required by the circuit. Each mask defines different parts of a transistor,
capacitor, resistor, or connector composing the complete integrated circuit and defines the circuitry
pattern for each layer on which the device is fabricated.
1Silicon Wafer.pdf (Size: 1.41 MB / Downloads: 40)
Introduction
The processing of Silicon wafers to produce integrated circuits involves a good deal of chemistry and
physics. In order to alter the surface conditions and properties, it is necessary to use both inert and toxic
chemicals, specific and unusual conditions, and to manipulate those conditions with both plasma-state
elements and with RF (Radio Frequency) energies. Starting with thin, round wafers of silicon crystal, in
diameters of 150, 200, and 300mm, the processes described here build up a succession of layers of
materials and geometries to produce thousands of electronic devices at tiny sizes, which together
function as integrated circuits (ICs). The devices which now occupy the surface of a one-inch square IC
would have occupied the better part of a medium-sized room 20 years ago, when all these devices
(transistors, resistors, capacitors, and so on) were only available as discreet units.
The conditions under which these processes can work to successfully transform the silicon into ICs
require an absolute absence of contaminants. Thus, the process chambers normally operate under
vacuum, with elemental, molecular, and other particulate contaminants rigorously controlled. In order to
understand these processes, then, we will begin the study of semiconductor processing with an overview
of vacuum systems and theory, of gas systems and theory, as applied specifically to these tools, and of
clean room processes and procedures
The semiconductor industry reflects and serves an extraordinary revolution in both materials science and
in data processing and storage. As recently as 1980, most individuals had no idea that computers would
ever impact their personal lives. Today, many families own one or two computers, and use many other
computers and dedicated processor systems in their appliances and automobiles. The intrusion of
electronics and computer technology into our lives and the devices we use daily is growing at an
exponential rate, and Moore’s Law still applied in the computer world. This is one of the few markets in
which, as time passes, the power and capacity of the products grows steadily, while the cost of that
power and capacity drops.
Thickness Sorting
Following slicing, silicon wafers are often sorted on an automated basis into
batches of uniform thickness to increase productivity in the next process step,
lapping. During thickness sorting, the wafer manufacturer can also identify defect
trends resulting from the slicing process.
Lapping & Etching Processes
Lapping removes the surface silicon which has been cracked or otherwise damaged
by the slicing process, and assures a flat surface. Wafers are then etched in a
chemically active reagent to remove any crystal damage remaining from the
previous process step.
Thickness Sorting and Flatness Checking
Following lapping or etching, silicon wafers are measured for flatness to identify and control defect
trends resulting from the lapping and etching processes. Wafers are also often sorted on an automated
basis according to thickness in order to increase productivity in the next process step, polishing.
Process Steps Details
In this sterile environment, the wafers are exposed to a multiple-step photolithography process that is
repeated once for each mask required by the circuit. Each mask defines different parts of a transistor,
capacitor, resistor, or connector composing the complete integrated circuit and defines the circuitry
pattern for each layer on which the device is fabricated.