Semiconductors: The Silicon Chip Essay examples -- science

Semiconductors: The Silicon Chip Silicon is the raw material most often used in integrated circuit (IC) fabrication. It is the second most abundant substance on the earth. It is extracted from rocks and common beach sand and put through an exhaustive purification process. In this form, silicon is the purist industrial substance that man produces, with impurities comprising less than one part in a billion. That is the equivalent of one tennis ball in a string of golf balls stretching from the earth to the moon. Semiconductors are usually materials which have energy-band gaps smaller than 2eV. An important property of semiconductors is the ability to change their resistivity over several orders of magnitude by doping. Semiconductors have electrical resistivities between 10-5 and 107 ohms. Semiconductors can be crystalline or amorphous. Elemental semiconductors are simple-element semiconductor materials such as silicon or germanium. Silicon is the most common semiconductor material used today. It is used for diodes, transistors, integrated circuits, memories, infrared detection and lenses, light-emitting diodes (LED), photosensors, strain gages, solar cells, charge transfer devices, radiation detectors and a variety of other devices. Silicon belongs to the group IV in the periodic table. It is a grey brittle material with a diamond cubic structure. Silicon is conventionally doped with Phosphorus, Arsenic and Antimony and Boron, Aluminum, and Gallium acceptors. The energy gap of silicon is 1.1 eV. This value permits the operation of silicon semiconductors devices at higher temperatures than germanium. Now I will give you some brief history of the evolution of electronics which will help you understand more about semiconductors and the silicon chip. In the early 1900’s before integrated circuits and silicon chips were invented, computers and radios were made with vacuum tubes. The vacuum tube was invented in 1906 by Dr.Lee DeForest. Throughout the first half of the 20th century, vacuum tubes were used to conduct, modulate and amplify electrical signals. They made possible a variety of new products including the radio and the computer. However vacuum tubes had some inherent problems. They were bulky, delicate and expensive, consumed a great deal of power, took time to warm up, got very hot, and eventually burned out. The first digital computer c... ..., the second mask pattern is exposed to the wafer, and the oxide is etched away to reveal new diffusion areas. The process is repeated for every mask - as many as 18 - needed to create a particular IC. Of critical importance here is the precise alignment of each mask over the wafer surface. It is out of alignment more than a fraction of a micrometer (one-millionth of a meter), the entire wafer is useless. During the last diffusion a layer of oxide is again grown over the water. Most of this oxide layer is left on the wafer to serve as an electrical insulator, and only small openings are etched through the oxide to expose circuit contact areas. To interconnect these areas, a thin layer of metal (usually aluminum) is deposited over the entire surface. The metal dips down into the circuit contact areas, touching the silicon. Most of the surface metal is then etched away, leaving an interconnection pattern between the circuit elements. The final layer is "vapox", or vapour-deposited- oxide, a glass-like material that protects the IC from contamination and damage. It, too, is etched away, but only above the "bonding pads", the square aluminum areas to which wires will later be attached. Semiconductors: The Silicon Chip Essay examples -- science Semiconductors: The Silicon Chip Silicon is the raw material most often used in integrated circuit (IC) fabrication. It is the second most abundant substance on the earth. It is extracted from rocks and common beach sand and put through an exhaustive purification process. In this form, silicon is the purist industrial substance that man produces, with impurities comprising less than one part in a billion. That is the equivalent of one tennis ball in a string of golf balls stretching from the earth to the moon. Semiconductors are usually materials which have energy-band gaps smaller than 2eV. An important property of semiconductors is the ability to change their resistivity over several orders of magnitude by doping. Semiconductors have electrical resistivities between 10-5 and 107 ohms. Semiconductors can be crystalline or amorphous. Elemental semiconductors are simple-element semiconductor materials such as silicon or germanium. Silicon is the most common semiconductor material used today. It is used for diodes, transistors, integrated circuits, memories, infrared detection and lenses, light-emitting diodes (LED), photosensors, strain gages, solar cells, charge transfer devices, radiation detectors and a variety of other devices. Silicon belongs to the group IV in the periodic table. It is a grey brittle material with a diamond cubic structure. Silicon is conventionally doped with Phosphorus, Arsenic and Antimony and Boron, Aluminum, and Gallium acceptors. The energy gap of silicon is 1.1 eV. This value permits the operation of silicon semiconductors devices at higher temperatures than germanium. Now I will give you some brief history of the evolution of electronics which will help you understand more about semiconductors and the silicon chip. In the early 1900’s before integrated circuits and silicon chips were invented, computers and radios were made with vacuum tubes. The vacuum tube was invented in 1906 by Dr.Lee DeForest. Throughout the first half of the 20th century, vacuum tubes were used to conduct, modulate and amplify electrical signals. They made possible a variety of new products including the radio and the computer. However vacuum tubes had some inherent problems. They were bulky, delicate and expensive, consumed a great deal of power, took time to warm up, got very hot, and eventually burned out. The first digital computer c... ..., the second mask pattern is exposed to the wafer, and the oxide is etched away to reveal new diffusion areas. The process is repeated for every mask - as many as 18 - needed to create a particular IC. Of critical importance here is the precise alignment of each mask over the wafer surface. It is out of alignment more than a fraction of a micrometer (one-millionth of a meter), the entire wafer is useless. During the last diffusion a layer of oxide is again grown over the water. Most of this oxide layer is left on the wafer to serve as an electrical insulator, and only small openings are etched through the oxide to expose circuit contact areas. To interconnect these areas, a thin layer of metal (usually aluminum) is deposited over the entire surface. The metal dips down into the circuit contact areas, touching the silicon. Most of the surface metal is then etched away, leaving an interconnection pattern between the circuit elements. The final layer is "vapox", or vapour-deposited- oxide, a glass-like material that protects the IC from contamination and damage. It, too, is etched away, but only above the "bonding pads", the square aluminum areas to which wires will later be attached.