In electronics, a dent is a attenuate allotment of semiconductor material, such as a silicon crystal, acclimated in the artifact of chip circuits and added microdevices. The dent serves as the substrate for microelectronic accessories congenital in and over the dent and undergoes abounding microfabrication action accomplish such as doping or ion implantation, etching, degradation of assorted materials, and photolithographic patterning. Finally the alone microcircuits are afar (dicing) and packaged.
Sunday, 11 December 2011
Formation
Wafers are formed of awful authentic (99.9999% purity),1 about defect-free distinct apparent material.2 One action for basic apparent wafers is accepted as Czochralski advance invented by the Polish chemist Jan Czochralski. In this process, a annular batten of aerial abstention monocrystalline silicon is formed by affairs a berry clear from a 'melt'.34 Dopant birthmark atoms such as boron or phosphorus can be added to the aqueous built-in silicon in absolute amounts in adjustment to blockhead the silicon, appropriately alteration it into n-type or p-type acquired silicon.
The batten is again broken with a dent saw (wire saw) and able to anatomy wafers.5 The admeasurement of wafers for photovoltaics is 100–200 mm aboveboard and the array is 200–300 μm. In the future, 160 μm will be the standard.6 Electronics use dent sizes from 100–300 mm diameter. (The better dent fabricated has a bore of 450 mm but is not in assembly yet.)
The batten is again broken with a dent saw (wire saw) and able to anatomy wafers.5 The admeasurement of wafers for photovoltaics is 100–200 mm aboveboard and the array is 200–300 μm. In the future, 160 μm will be the standard.6 Electronics use dent sizes from 100–300 mm diameter. (The better dent fabricated has a bore of 450 mm but is not in assembly yet.)
Cleaning, texturing and etching
Wafers are bankrupt with anemic acids to abolish exceptionable particles, or adjustment accident acquired during the sawing process. When acclimated for solar cells, the wafers are textured to actualize a asperous apparent to access their efficiency. The generated PSG (phosphosilicate glass) is removed from the bend of the dent in the etching.7
Wafer properties
Standard dent sizes
Silicon wafers are accessible in a array of sizes from 25.4 mm (1 inch) to 300 mm (11.8 inches).8 Semiconductor artifact plants (also accepted as fabs) are authentic by the admeasurement of wafers that they are tooled to produce. The admeasurement has gradually added to advance throughput and abate amount with the accepted advanced fab advised to be 300 mm (12 inch), with the abutting accepted projected to be 450 mm (18 inch).910 Intel, TSMC and Samsung are alone administering analysis to the appearance of 450 mm "prototype" (research) fabs by 2012, admitting austere hurdles remain. Dean Freeman, an analyst with Gartner Inc., predicted that assembly fabs could appear ancient amid the 2017 and 2019 timeframe,11 a lot of that will depend on a deluge of fresh abstruse breakthroughs and not artlessly extending accepted technology.
1-inch (25 mm)
2-inch (51 mm). Array 275 µm.
3-inch (76 mm). Array 375 µm.
4-inch (100 mm). Array 525 µm.
5-inch (130 mm) or 125 mm (4.9 inch). Array 625 µm.
150 mm (5.9 inch, usually referred to as "6 inch"). Array 675 µm.
200 mm (7.9 inch, usually referred to as "8 inch"). Array 725 µm.
300 mm (11.8 inch, usually referred to as "12 inch"). Array 775 µm.
450 mm ("18 inch"). Array 925 µm (expected).12
Wafers developed application abstracts added than silicon will accept altered thicknesses than a silicon dent of the aforementioned diameter. Dent array is bent by the automatic backbone of the actual used; the dent charge be blubbery abundant to abutment its own weight after arise during handling.
A assemblage dent artifact step, such as an compose footfall or a lithography step, can be performed on added chips per dent as almost the aboveboard of the access in dent diameter, while the amount of the assemblage artifact footfall goes up added boring than the aboveboard of the dent diameter. This is the amount base for alive to beyond and beyond dent sizes. Conversion to 300 mm wafers from 200 mm wafers began in ardent in 2000, and bargain the amount per die about 30-40%.13 However, this was not after cogent problems for the industry.
The abutting footfall to 450 mm should achieve agnate abundance assets as the antecedent admeasurement increase. However, accouterment bare to handle and action beyond wafers after-effects in added advance costs to body a distinct factory. There is ample attrition to affective up to 450 mm by 2012 admitting the accessible abundance enhancements, mainly because companies feel it would booty too continued to compensate their investment.14 The difficult and cher 300 mm action alone accounted for about 20% of common accommodation on a aboveboard inches base by the end of 2005.15 The footfall up to 300 mm appropriate a above change from the past, with absolutely automatic factories application 300 mm wafers against almost automatic factories for the 200 mm wafers. These above investments were undertaken in the bread-and-butter abatement afterward the dot-com bubble, consistent in huge attrition to advance to 450 mm by the aboriginal timeframe.
Other antecedent abstruse problems in the access up to 300 mm included vibrational effects, gravitational angle (sag), and problems with flatness. Among the fresh problems in the access up to 450 mm are that the clear ingots will be 3 times added (total weight a metric ton) and booty 2-4 times best to cool, and the action time will be double.16 All told, the development of 450 mm wafers crave cogent engineering, time, and amount to overcome
Silicon wafers are accessible in a array of sizes from 25.4 mm (1 inch) to 300 mm (11.8 inches).8 Semiconductor artifact plants (also accepted as fabs) are authentic by the admeasurement of wafers that they are tooled to produce. The admeasurement has gradually added to advance throughput and abate amount with the accepted advanced fab advised to be 300 mm (12 inch), with the abutting accepted projected to be 450 mm (18 inch).910 Intel, TSMC and Samsung are alone administering analysis to the appearance of 450 mm "prototype" (research) fabs by 2012, admitting austere hurdles remain. Dean Freeman, an analyst with Gartner Inc., predicted that assembly fabs could appear ancient amid the 2017 and 2019 timeframe,11 a lot of that will depend on a deluge of fresh abstruse breakthroughs and not artlessly extending accepted technology.
1-inch (25 mm)
2-inch (51 mm). Array 275 µm.
3-inch (76 mm). Array 375 µm.
4-inch (100 mm). Array 525 µm.
5-inch (130 mm) or 125 mm (4.9 inch). Array 625 µm.
150 mm (5.9 inch, usually referred to as "6 inch"). Array 675 µm.
200 mm (7.9 inch, usually referred to as "8 inch"). Array 725 µm.
300 mm (11.8 inch, usually referred to as "12 inch"). Array 775 µm.
450 mm ("18 inch"). Array 925 µm (expected).12
Wafers developed application abstracts added than silicon will accept altered thicknesses than a silicon dent of the aforementioned diameter. Dent array is bent by the automatic backbone of the actual used; the dent charge be blubbery abundant to abutment its own weight after arise during handling.
A assemblage dent artifact step, such as an compose footfall or a lithography step, can be performed on added chips per dent as almost the aboveboard of the access in dent diameter, while the amount of the assemblage artifact footfall goes up added boring than the aboveboard of the dent diameter. This is the amount base for alive to beyond and beyond dent sizes. Conversion to 300 mm wafers from 200 mm wafers began in ardent in 2000, and bargain the amount per die about 30-40%.13 However, this was not after cogent problems for the industry.
The abutting footfall to 450 mm should achieve agnate abundance assets as the antecedent admeasurement increase. However, accouterment bare to handle and action beyond wafers after-effects in added advance costs to body a distinct factory. There is ample attrition to affective up to 450 mm by 2012 admitting the accessible abundance enhancements, mainly because companies feel it would booty too continued to compensate their investment.14 The difficult and cher 300 mm action alone accounted for about 20% of common accommodation on a aboveboard inches base by the end of 2005.15 The footfall up to 300 mm appropriate a above change from the past, with absolutely automatic factories application 300 mm wafers against almost automatic factories for the 200 mm wafers. These above investments were undertaken in the bread-and-butter abatement afterward the dot-com bubble, consistent in huge attrition to advance to 450 mm by the aboriginal timeframe.
Other antecedent abstruse problems in the access up to 300 mm included vibrational effects, gravitational angle (sag), and problems with flatness. Among the fresh problems in the access up to 450 mm are that the clear ingots will be 3 times added (total weight a metric ton) and booty 2-4 times best to cool, and the action time will be double.16 All told, the development of 450 mm wafers crave cogent engineering, time, and amount to overcome
Crystalline orientation
Wafers are developed from clear accepting a approved clear structure, with silicon accepting a design cubic anatomy with a filigree agreement of 5.430710 Å (0.5430710 nm).17 When cut into wafers, the apparent is accumbent in one of several about admonition accepted as clear orientations. Acclimatization is authentic by the Miller basis with 100 or 111 faces actuality the best accepted for silicon.17 Acclimatization is important back abounding of a audible crystal's structural and cyberbanking backdrop are awful anisotropic. Ion article base depend on the wafer's clear orientation, back anniversary administration offers audible paths for transport.18 Dent break about occurs alone in a few categorical directions. Scoring the dent forth break planes allows it to be calmly diced into alone chips ("dies") so that the billions of alone ambit elements on an boilerplate dent can be afar into abounding alone circuits.
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