20:
556:
vertically in the tube the convection and the temperature gradient with it causes the top of the wafer to have a thicker oxide than the bottom of the wafer. Vertical furnaces solve this problem by having wafer sitting horizontally, and then having the gas flow in the furnace flowing from top to bottom, significantly damping any thermal convections.
640:, which blocks diffusion of oxygen and water vapor due to its oxidation at a much slower rate. The nitride is removed after oxidation is complete. This process cannot produce sharp features, because lateral (parallel to the surface) diffusion of oxidant molecules under the nitride mask causes the oxide to protrude into the masked area.
543:
rack (called a "boat"). Historically, the boat entered the oxidation chamber from the side (this design is called "horizontal"), and held the wafers vertically, beside each other. However, many modern designs hold the wafers horizontally, above and below each other, and load them into the oxidation
266:
Thermal oxide incorporates silicon consumed from the substrate and oxygen supplied from the ambient. Thus, it grows both down into the wafer and up out of it. For every unit thickness of silicon consumed, 2.17 unit thicknesses of oxide will appear. If a bare silicon surface is oxidized, 46% of the
555:
Vertical furnaces also eliminate an issue that plagued horizontal furnaces: non-uniformity of grown oxide across the wafer. Horizontal furnaces typically have convection currents inside the tube which causes the bottom of the tube to be slightly colder than the top of the tube. As the wafers lie
393:
that already contains oxide is placed in an oxidizing ambient, this equation must be modified by adding a corrective term Ď„, the time that would have been required to grow the pre-existing oxide under current conditions. This term may be found using the equation for
817:
J. Appels, E. Kooi, M. M. Paffen, J. J. H. Schatorje, and W. H. C. G. Verkuylen, “Local oxidation of silicon and its application in semiconductor-device technology,” PHILIPS RESEARCH Reports, vol. 25, no. 2, pp. 118–132, Apr.
373:
193:
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contamination. Unlike horizontal furnaces, in which falling dust can contaminate any wafer, vertical furnaces use enclosed cabinets with air filtration systems to prevent dust from reaching the wafers.
254:
632:
Thermal oxidation can be performed on selected areas of a wafer, and blocked on others. This process, first developed at
Philips, is commonly referred to as the local oxidation of silicon (
827:
A. Kuiper, M. Willemsen, J. M. G. Bax, and F. H. P. H. Habraken, “Oxidation behaviour of LPCVD silicon oxynitride films,” Applied
Surface Science, vol. 33, no. 34, pp. 757–764, Oct. 1988.
586:
The long time required to grow a thick oxide in dry oxidation makes this process impractical. Thick oxides are usually grown with a long wet oxidation bracketed by short dry ones (a
525:
681:
processes, thermal oxidation is never performed after the doping for the source and drain terminals is performed, because it would disturb the placement of the dopants.
51:. The technique forces an oxidizing agent to diffuse into the wafer at high temperature and react with it. The rate of oxide growth is often predicted by the
559:
Vertical furnaces also allow the use of load locks to purge the wafers with nitrogen before oxidation to limit the growth of native oxide on the Si surface.
84:
24:
590:
cycle). The beginning and ending dry oxidations produce films of high-quality oxide at the outer and inner surfaces of the oxide layer, respectively.
378:
where the constants A and B relate to properties of the reaction and the oxide layer, respectively. This model has further been adapted to account for
298:
677:
at about 600 °C). However, the high temperatures required to produce High
Temperature Oxide (HTO) restrict its usability. For instance, in
651:. This redistribution is governed by the segregation coefficient, which determines how strongly the oxide absorbs or rejects the dopant, and the
748:
567:
Wet oxidation is preferred to dry oxidation for growing thick oxides, because of the higher growth rate. However, fast oxidation leaves more
547:
Because vertical furnaces stand higher than horizontal furnaces, they may not fit into some microfabrication facilities. They help to prevent
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for electrons and allow current to leak along the interface. (This is called a "dirty" interface.) Wet oxidation also yields a lower-
105:
539:, at temperatures between 800 and 1200 °C. A single furnace accepts many wafers at the same time, in a specially designed
853:
199:
885:
414:
869:
Online calculator including deal grove and massoud oxidation models, with pressure and doping effects at:
55:. Thermal oxidation may be applied to different materials, but most commonly involves the oxidation of
666:) oxidizes more slowly than a <111> wafer, but produces an electrically cleaner oxide interface.
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Thermal oxidation of any variety produces a higher-quality oxide, with a much cleaner interface, than
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390:
19:
707:"Two-dimensional modeling of the self-limiting oxidation in silicon and tungsten nanowires"
52:
8:
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48:
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71:
Thermal oxidation of silicon is usually performed at a temperature between 800 and 1200
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differently in silicon and oxide, a growing oxide will selectively take up or reject
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368:{\displaystyle \tau ={\frac {X_{o}^{2}}{B}}+{\frac {X_{o}}{({\frac {B}{A}})}}}
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845:
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to the oxidizing medium. Its presence also increases the rate of oxidation.
572:
568:
382:
oxidation processes, as used for the fabrication and morphological design of
636:) process. Areas which are not to be oxidized are covered with a film of
263:(HCl). The chlorine neutralizes metal ions that may occur in the oxide.
80:
267:
oxide thickness will lie below the original surface, and 54% above it.
644:
723:
609:
659:
576:
188:{\displaystyle {\rm {Si+2H_{2}O\rightarrow SiO_{2}+2H_{2\ (g)}}}}
72:
56:
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of oxide resulting in low temperature oxide layer (reaction of
648:
605:
601:
540:
88:
633:
594:
40:
292:, at a constant temperature, on a bare silicon surface, is:
840:
Jaeger, Richard C. (2001). "Thermal
Oxidation of Silicon".
548:
281:
According to the commonly used Deal-Grove model, the time
259:
The oxidizing ambient may also contain several percent of
16:
Process creating a thin layer of (usually) silicon dioxide
597:
798:
University of
Kentucky Center for Nanoscale Engineering
871:
http://www.lelandstanfordjunior.com/thermaloxide.html
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301:
249:{\displaystyle {\rm {Si+O_{2}\rightarrow SiO_{2}\,}}}
202:
108:
23:
Furnaces used for diffusion and thermal oxidation at
519:
367:
248:
187:
99:oxidation. The reaction is one of the following:
91:as the oxidant; it is consequently called either
877:
662:affects oxidation. A <100> wafer (see
842:Introduction to Microelectronic Fabrication
27:technological facility in Toulouse, France.
616:. Chlorine is often introduced by adding
732:
722:
711:Theoretical and Applied Mechanics Letters
243:
571:at the silicon interface, which produce
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18:
535:Most thermal oxidation is performed in
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520:{\displaystyle X_{o}(t)=A/2\cdot \left}
285:required to grow an oxide of thickness
878:
839:
778:: CS1 maint: archived copy as title (
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608:is of particular concern). However,
39:is a way to produce a thin layer of
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401:Solving the quadratic equation for
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612:can immobilize sodium by forming
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658:The orientation of the silicon
79:layer (HTO). It may use either
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705:Liu, M.; et al. (2016).
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600:can degrade performance of
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734:10.1016/j.taml.2016.08.002
386:and other nanostructures.
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671:chemical vapor deposition
75:, resulting in so called
886:Semiconductor technology
844:. Upper Saddle River:
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369:
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77:High Temperature Oxide
59:substrates to produce
47:) on the surface of a
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67:The chemical reaction
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544:chamber from below.
531:Oxidation technology
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643:Because impurities
581:dielectric strength
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579:oxide, with lower
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855:978-0-201-44494-0
622:trichloroethylene
618:hydrogen chloride
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261:hydrochloric acid
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37:thermal oxidation
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53:Deal–Grove model
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901:Microtechnology
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749:"Archived copy"
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638:silicon nitride
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614:sodium chloride
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87:) or molecular
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61:silicon dioxide
45:silicon dioxide
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717:(5): 195–199.
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664:Miller indices
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761:on 2015-01-21
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801:. Retrieved
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384:Si nanowires
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36:
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653:diffusivity
628:Other notes
588:dry-wet-dry
81:water vapor
880:Categories
794:"Furnaces"
765:2013-07-07
724:1911.08908
685:References
896:Materials
507:−
499:τ
452:⋅
303:τ
225:→
137:→
85:UHP steam
83:(usually
43:(usually
774:cite web
645:dissolve
610:chlorine
537:furnaces
408:yields:
916:Silicon
906:MOSFETs
834:Sources
660:crystal
649:dopants
602:MOSFETs
593:Mobile
577:density
398:above.
57:silicon
852:
679:MOSFET
606:sodium
541:quartz
170:
89:oxygen
818:1970.
803:7 May
759:(PDF)
752:(PDF)
719:arXiv
690:Notes
634:LOCOS
595:metal
391:wafer
389:If a
49:wafer
41:oxide
850:ISBN
805:2023
780:link
675:TEOS
598:ions
549:dust
25:LAAS
729:doi
620:or
97:dry
95:or
93:wet
31:In
882::
848:.
796:.
776:}}
772:{{
727:.
713:.
709:.
697:^
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73:°C
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737:.
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283:Ď„
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
