Gas phase surface preparation and activation of silicon using ultraviolet activated chemistries

Persistent Link:
http://hdl.handle.net/10150/280695
Title:
Gas phase surface preparation and activation of silicon using ultraviolet activated chemistries
Author:
Finstad, Casey Charles
Issue Date:
2004
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Microelectronic devices have been scaled down to the point where lateral dimensions are on the order of a hundred atoms and a film thicknesses might be less than ten atoms. This makes surface preparation an increasingly important part of the fabrication process. The atoms and molecules terminating surfaces between processing steps are now a relatively large fraction of the overall film thickness. These terminating monolayers have to function as passivation layers, diffusion barriers, and seed layers for subsequent thin film depositions. This work demonstrates that precise control of the atoms and molecules on a silicon surface can be achieved using gas phase processes. The Research Cluster Apparatus (RCA) was built with a reactor for oxide removal using hydrofluoric acid and water vapor (HF/vapor), and a reactor for the removal of metallic and organic contaminates using ultraviolet activated chlorine gas (UV-Cl₂). Both reactors were integrated via high vacuum with a surface analysis chamber so samples could be characterized without atmospheric exposure. The capabilities of the system were demonstrated by using an HF/vapor (100 Torr, 27°C, 200 s) and UV-Cl₂ (10 Torr Cl₂, 90°C, 15 min) sequence to remove a mixed oxide/fluorocarbon residue, characteristic of contamination generated by reactive ion etching (RIE). To demonstrate the metals removal capability, oxidized copper was cleaned from silicon. The UV-Cl₂ chemistry leaves the surface terminated with chlorine atoms, rather than hydrogen, promoting a deposition reaction with ammonia (1-1000 Torr, 75°C, 5-60 min) to produce a surface terminated with up to 0.3 monolayers of surface amine groups, as measured by XPS. The highly polar N-H bonds of surface amines can be used as a seed layer to promote nucleation of high-k dielectric films deposited on silicon using atomic layer deposition (ALD). To enhance the deposition of the amines, photolysis (λ < 217 nm) of gas phase ammonia (UV-NH₃) generated NH₂ photofragments that reacted with hydrogen terminated Si(100), saturating at up to 1.7 ML (10 Torr NH₃, 75°C, 35 mW/cm²). These processes help enable further miniaturization by adding another mechanism for atomic-level manipulation of surface properties to the nanotechnology toolbox.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Chemistry, General.; Engineering, Chemical.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemical and Environmental Engineering
Degree Grantor:
University of Arizona
Advisor:
Muscat, Anthony J.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleGas phase surface preparation and activation of silicon using ultraviolet activated chemistriesen_US
dc.creatorFinstad, Casey Charlesen_US
dc.contributor.authorFinstad, Casey Charlesen_US
dc.date.issued2004en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractMicroelectronic devices have been scaled down to the point where lateral dimensions are on the order of a hundred atoms and a film thicknesses might be less than ten atoms. This makes surface preparation an increasingly important part of the fabrication process. The atoms and molecules terminating surfaces between processing steps are now a relatively large fraction of the overall film thickness. These terminating monolayers have to function as passivation layers, diffusion barriers, and seed layers for subsequent thin film depositions. This work demonstrates that precise control of the atoms and molecules on a silicon surface can be achieved using gas phase processes. The Research Cluster Apparatus (RCA) was built with a reactor for oxide removal using hydrofluoric acid and water vapor (HF/vapor), and a reactor for the removal of metallic and organic contaminates using ultraviolet activated chlorine gas (UV-Cl₂). Both reactors were integrated via high vacuum with a surface analysis chamber so samples could be characterized without atmospheric exposure. The capabilities of the system were demonstrated by using an HF/vapor (100 Torr, 27°C, 200 s) and UV-Cl₂ (10 Torr Cl₂, 90°C, 15 min) sequence to remove a mixed oxide/fluorocarbon residue, characteristic of contamination generated by reactive ion etching (RIE). To demonstrate the metals removal capability, oxidized copper was cleaned from silicon. The UV-Cl₂ chemistry leaves the surface terminated with chlorine atoms, rather than hydrogen, promoting a deposition reaction with ammonia (1-1000 Torr, 75°C, 5-60 min) to produce a surface terminated with up to 0.3 monolayers of surface amine groups, as measured by XPS. The highly polar N-H bonds of surface amines can be used as a seed layer to promote nucleation of high-k dielectric films deposited on silicon using atomic layer deposition (ALD). To enhance the deposition of the amines, photolysis (λ < 217 nm) of gas phase ammonia (UV-NH₃) generated NH₂ photofragments that reacted with hydrogen terminated Si(100), saturating at up to 1.7 ML (10 Torr NH₃, 75°C, 35 mW/cm²). These processes help enable further miniaturization by adding another mechanism for atomic-level manipulation of surface properties to the nanotechnology toolbox.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectChemistry, General.en_US
dc.subjectEngineering, Chemical.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemical and Environmental Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMuscat, Anthony J.en_US
dc.identifier.proquest3158090en_US
dc.identifier.bibrecord.b4790818xen_US
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