Application of atomic layer deposited thin films to silicon detectors

Jennifer Ott

Application of atomic layer deposited thin films to silicon detectors

Julkaisun otsikon käännös: Atomikerroskasvatuksella tuotettujen ohutkalvojen soveltaminen puolijohdeilmaisimiin

Jennifer Ott

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Piitä käytetään laajasti erilaisissa säteily- ja hiukkasilmaisimissa sen matalan hinnan, hyvän saatavuuden ja valmistettavuuden takia. Piistä valmistettuja pikseli-ilmaisimia käytetään myös hiukkasten ratojen määrittämiseen korkeaenergiafysiikan kokeissa, mukaanlukien kaikissa Suuren Hadronitörmäyttimen (Large Hadron Collider, LHC) koeasemissa. Näissä vallitsevat hyvin haastavat olosuhteet pii-ilmaisimille, erityisesti korkeiden säteilytasojen muodossa. Lisäksi ilmaisimilta edellytetään hyvä paikkaresoluutio ja nopeaa signaalinmuodostusta LHC:n 40 MHz:ntaajuudessa. Tämä tutkielma käsittelee atomikerroskasvatus -menetelmällä (atomic layer deposition, ALD) kasvatettujen alumiinioksidiohutkalvojen (Al2O3) käyttöä pii-pikseli-ilmaisimissa eristeenä ja pintapassivointina. Negatiivisen oksidivarauksensa vuoksi tämä materiaali on lupaava vaihtoehto yleisesti käytetylle piioksidille (SiO2) ja eristävälle ioni-implantoinnille korkean paikkaresoluution pikseli-ilmaisimissa, jollaisia kehitetään useisiin tuleviin koeasemien päivityksiin ja kokonaan uusiin hiukkasfysiikan kokeisiin. Tässä esitetyssä lähestymistavassa pyritään myös vähentämään säteilyn aiheuttamaa pii-ilmaisimen toimintakyvyn heikkenemistä käyttämällä kapasitiivisesti kytkettyjä ilmaisimia, joissa Al2O3 toimii kytkintäeristeenä ja kuvioitu titaaninitridikalvo bias-vastuksena. Aluksi tutkitaan Al2O3-ohutkalvojen pintapassivointia ja sähköisiä ominaisuuksia n- ja p-tyypin float zone -piissä kasvatuksen jälkeisen lämpökäsittelyn lämpötilan funktiona. P-tyypin Czochralski-piissä, joka on tämän tutkimuksen ensisijainen kohdemateriaali pikseli-ilmaisimille, eri hapen lähtöaineella kasvatettuja Al2O3-ohutkalvoja tutkitaan ensin kontaktittomilla karakterisointimenetelmillä ja myöhemmin diodeissa ja MOS-kondensaattoreissa. Vaikka perinteisesti käytetty vesi lähtöaineena tarjoaa korkeimmat rekombinaatioelinajat sekä parhaat läpilyöntiominaisuudet diodeissa, näin kasvatettujen kalvojen oksidivaraus jää verrattain matalaksi ja kompensoituu nopeasti positiiviseksi gammasäteilytyksen vaikutuksesta. Otsonilla kasvatetuilla kalvoilla varaus on korkeampi ja sen säteilynkestävyys on parempi. Ottaen huomioon kaikki näin saadut tulokset, veden ja otsonin yhdistelmä osoittautuu tässä tapauksessa parhaaksi hapen lähtöaineeksi ALD:ssa. Tämän lisäksi tutkitaan tarkemmin vedellä kasvatetuissa Al2O3-kalvoissa esiintyvää blisteröintiä ja esitellään uusia havaintoja tämän ilmiön kytkeytymisestä piisubstraatin dopaukseen. Lopuksi kuvaillaan pikseli-ilmaisimien prosessointia, kiinnittäen erityistä huomiota ALD-prosessivaiheisiin, sintrauslämpötilaan sekä TiN -vastusten valmistamiseen. Pikseli-ilmaisimissa alumiinioksidia kasvatetaan vesi-otsoni -lähdeaineyhdistelmällä perustuen yllä mainittuihin materiaalitason tuloksiin. Ilmaisimien flip-chip -bondaus CMS PSI46dig -lukuelektroniikkasiruun ja niiden testaaminen radioaktiivisilla lähteillä vahvistavat, että AC-kytketyt alumiinioksidia hyödyntävät pikseli-ilmaisimet soveltuvat korkeaenergiafysiikan jälki-ilmaisimiksi.

Julkaisun otsikon käännös	Atomikerroskasvatuksella tuotettujen ohutkalvojen soveltaminen puolijohdeilmaisimiin
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Savin, Hele, Vastuuprofessori Luukka, Panja, Ohjaaja, Ulkoinen henkilö Härkönen, Jaakko, Ohjaaja, Ulkoinen henkilö
Kustantaja	Aalto University
Painoksen ISBN	978-952-64-0276-5
Sähköinen ISBN	978-952-64-0277-2
Tila	Julkaistu - 2021
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

pii
pikseli-ilmaisin
säteilynkestävyys
atomikerroskasvatus
alumiinioksidi

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-64-0277-2

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Repo, P. (Manager) & Rissanen, A. (Other)
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@phdthesis{b20f68d3cf424d7c852c01f5098d2692,

title = "Application of atomic layer deposited thin films to silicon detectors",

abstract = "Silicon is used in a variety of semiconductor radiation and particle detectors due to its reasonable cost, good availability and processability, and performance at room temperature. Pixel detectors made of silicon are used for particle tracking at different high-energy physics experiments, including all large experiments at the LHC. The planned upgrades of the tracking detectors of the LHC experiments, e.g. the CMS Inner Tracker, as well as experiments at future colliders, are a very challenging environment for silicon detectors due to their extreme radiation levels, combined with high occupancies, fast readout and high segmentation of the sensors. This thesis features the application of aluminium oxide thin films grown by atomic layer deposition as field insulation and surface passivation in silicon pixel detectors. This approach aims to mitigate some of the radiation-induced damage on detectors, as well as reduce high-temperature fabrication steps, by using AC-coupled sensors with Al2O3 as insulator and high-k coupling dielectric and TiN biasing resistors. Surface passivation and electrical properties of Al2O3 films deposited on high-resistivity silicon are studied on n- and p-type FZ-silicon at different post-deposition anneal temperatures. On magnetic Czochralski silicon, which is the target material for the pixel detectors discussed in this work, Al2O3 films deposited with different oxidants in ALD are studied first with the same contactless characterization methods, and later in diode and MOS capacitor devices. While traditional H2O as oxidant provides the best recombination lifetimes, as well as the best breakdown properties in diodes, the oxide charge achieved with this ALD process is comparatively low and is compensated in gamma irradiation. Films deposited using O3 exhibit higher charge and better radiation hardness, and considering all experiments, a combination of H2O and O3 is identified as the best choice of ALD oxidant. In addition, the phenomenon of blistering in AlOx films deposited with H2O is investigated in more detail, and new observations on the influence of substrate doping on blistering are shown. Processing of pixel detectors is described with an emphasis on the ALD steps, and also noting on post-anneal temperature and TiN bias resistor fabrication. For pixel detectors, Al2O3 is deposited with oxidants H2O+O3 based on the earlier results. Finally, pixel detectors are flip-chip bonded to the CMS PSI46dig readout chip and tested with radioactive sources, confirming their functionality. It is concluded that ALD-grown Al2O3 films are a promising alternative to SiO2 and insulating implants for small-pitch silicon pixel detectors, which are under development for a variety of future collider physics experiments.",

keywords = "silicon, pixel detector, radiation hardness, atomic layer deposition, aluminium oxide, pii, pikseli-ilmaisin, s{\"a}teilynkest{\"a}vyys, atomikerroskasvatus, alumiinioksidi, silicon, pixel detector, radiation hardness, atomic layer deposition, aluminium oxide",

author = "Jennifer Ott",

year = "2021",

language = "English",

isbn = "978-952-64-0276-5",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "22",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Application of atomic layer deposited thin films to silicon detectors

AU - Ott, Jennifer

PY - 2021

Y1 - 2021

N2 - Silicon is used in a variety of semiconductor radiation and particle detectors due to its reasonable cost, good availability and processability, and performance at room temperature. Pixel detectors made of silicon are used for particle tracking at different high-energy physics experiments, including all large experiments at the LHC. The planned upgrades of the tracking detectors of the LHC experiments, e.g. the CMS Inner Tracker, as well as experiments at future colliders, are a very challenging environment for silicon detectors due to their extreme radiation levels, combined with high occupancies, fast readout and high segmentation of the sensors. This thesis features the application of aluminium oxide thin films grown by atomic layer deposition as field insulation and surface passivation in silicon pixel detectors. This approach aims to mitigate some of the radiation-induced damage on detectors, as well as reduce high-temperature fabrication steps, by using AC-coupled sensors with Al2O3 as insulator and high-k coupling dielectric and TiN biasing resistors. Surface passivation and electrical properties of Al2O3 films deposited on high-resistivity silicon are studied on n- and p-type FZ-silicon at different post-deposition anneal temperatures. On magnetic Czochralski silicon, which is the target material for the pixel detectors discussed in this work, Al2O3 films deposited with different oxidants in ALD are studied first with the same contactless characterization methods, and later in diode and MOS capacitor devices. While traditional H2O as oxidant provides the best recombination lifetimes, as well as the best breakdown properties in diodes, the oxide charge achieved with this ALD process is comparatively low and is compensated in gamma irradiation. Films deposited using O3 exhibit higher charge and better radiation hardness, and considering all experiments, a combination of H2O and O3 is identified as the best choice of ALD oxidant. In addition, the phenomenon of blistering in AlOx films deposited with H2O is investigated in more detail, and new observations on the influence of substrate doping on blistering are shown. Processing of pixel detectors is described with an emphasis on the ALD steps, and also noting on post-anneal temperature and TiN bias resistor fabrication. For pixel detectors, Al2O3 is deposited with oxidants H2O+O3 based on the earlier results. Finally, pixel detectors are flip-chip bonded to the CMS PSI46dig readout chip and tested with radioactive sources, confirming their functionality. It is concluded that ALD-grown Al2O3 films are a promising alternative to SiO2 and insulating implants for small-pitch silicon pixel detectors, which are under development for a variety of future collider physics experiments.

AB - Silicon is used in a variety of semiconductor radiation and particle detectors due to its reasonable cost, good availability and processability, and performance at room temperature. Pixel detectors made of silicon are used for particle tracking at different high-energy physics experiments, including all large experiments at the LHC. The planned upgrades of the tracking detectors of the LHC experiments, e.g. the CMS Inner Tracker, as well as experiments at future colliders, are a very challenging environment for silicon detectors due to their extreme radiation levels, combined with high occupancies, fast readout and high segmentation of the sensors. This thesis features the application of aluminium oxide thin films grown by atomic layer deposition as field insulation and surface passivation in silicon pixel detectors. This approach aims to mitigate some of the radiation-induced damage on detectors, as well as reduce high-temperature fabrication steps, by using AC-coupled sensors with Al2O3 as insulator and high-k coupling dielectric and TiN biasing resistors. Surface passivation and electrical properties of Al2O3 films deposited on high-resistivity silicon are studied on n- and p-type FZ-silicon at different post-deposition anneal temperatures. On magnetic Czochralski silicon, which is the target material for the pixel detectors discussed in this work, Al2O3 films deposited with different oxidants in ALD are studied first with the same contactless characterization methods, and later in diode and MOS capacitor devices. While traditional H2O as oxidant provides the best recombination lifetimes, as well as the best breakdown properties in diodes, the oxide charge achieved with this ALD process is comparatively low and is compensated in gamma irradiation. Films deposited using O3 exhibit higher charge and better radiation hardness, and considering all experiments, a combination of H2O and O3 is identified as the best choice of ALD oxidant. In addition, the phenomenon of blistering in AlOx films deposited with H2O is investigated in more detail, and new observations on the influence of substrate doping on blistering are shown. Processing of pixel detectors is described with an emphasis on the ALD steps, and also noting on post-anneal temperature and TiN bias resistor fabrication. For pixel detectors, Al2O3 is deposited with oxidants H2O+O3 based on the earlier results. Finally, pixel detectors are flip-chip bonded to the CMS PSI46dig readout chip and tested with radioactive sources, confirming their functionality. It is concluded that ALD-grown Al2O3 films are a promising alternative to SiO2 and insulating implants for small-pitch silicon pixel detectors, which are under development for a variety of future collider physics experiments.

KW - silicon

KW - pixel detector

KW - radiation hardness

KW - atomic layer deposition

KW - aluminium oxide

KW - pii

KW - pikseli-ilmaisin

KW - säteilynkestävyys

KW - atomikerroskasvatus

KW - alumiinioksidi

KW - silicon

KW - pixel detector

KW - radiation hardness

KW - atomic layer deposition

KW - aluminium oxide

M3 - Doctoral Thesis

SN - 978-952-64-0276-5

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Application of atomic layer deposited thin films to silicon detectors

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