Endre søk
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Formation of pn junctions in deep silicon pores for X-ray imaging detector applications
KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.ORCID-id: 0000-0002-5260-5322
KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
2003 (engelsk)Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 509, nr 1-3, s. 96-101Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The formation of pn junctions in deep silicon pores has been studied for a new concept of X-ray imaging detectors. The sensitive part of the device is an array of CsI(Tl) columns formed by filling a silicon matrix of pores having pn junctions in their walls. Under X-ray illumination, the CsI(TI) scintillator emits photons that are collected by the pn junctions. Relatively high signal collection efficiency is expected. However, the formation of pn junctions inside pore walls represents a challenging step in the detector fabrication. In this work pore matrices were fabricated in n-type silicon by deep reactive ion etching and by photo-electrochemical etching. The pn junctions were formed either by boron diffusion or deposition of boron doped poly-silicon. Various techniques were used to analyze the transverse depth profiles of boron atoms at different pore depths. The study shows successful results for pn-junctions formed both by diffusion and by poly-silicon deposition.

sted, utgiver, år, opplag, sider
2003. Vol. 509, nr 1-3, s. 96-101
Emneord [en]
pn junction, SCM, SEM, Silicon macropores, SIMS, SSRM, Photons, Porosity, Semiconductor junctions, X rays, X-ray imaging detectors, Radiation detectors
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-4961DOI: 10.1016/S0168-9002(03)01556-0ISI: 000185047700017OAI: oai:DiVA.org:kth-4961DiVA, id: diva2:7218
Merknad
QC 20100831Tilgjengelig fra: 2005-03-03 Laget: 2005-03-03 Sist oppdatert: 2017-12-05bibliografisk kontrollert
Inngår i avhandling
1. Electrochemically etched pore arrays in silicon for X-ray imaging detectors
Åpne denne publikasjonen i ny fane eller vindu >>Electrochemically etched pore arrays in silicon for X-ray imaging detectors
2005 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Digital devices have now been introduced in many X-ray imaging applications, replacing slowly traditional photographic films. These devices are preferred as they offer real time imaging, easy handling and fast treatment of the images. However, the performance of the detectors still have to be improved in order to increase the image quality, and possibly reduce the X-ray dose, a vital parameter for medical use. In this thesis, three different new detector concepts have been investigated. All designs use pore arrays, which are ideal starting structures to form pixellated detectors.

Electrochemical etching of n-type silicon in aqueous hydrofluoric acid solution (HF) has been studied to form these pore arrays. A broad range of pores have been fabricated with diameters varying from 200 nm to 40 µm and with depths reaching almost the wafer thickness, thus leading to very high aspect ratios. The technique was also found to be suitable for the formation of other types of structures such as pillars and tubes on the sub micrometer scale. The etching is based on the dissolution of silicon in HF under anodic bias and a supply of positive electrical carriers (holes). As holes are the minority carriers in n-type silicon, they are usually photo-generated. In this work an alternative technique, based on hole injection from a forward-biased pn junction, has been successfully pioneered.

The first X-ray imaging detector concept presented in the thesis consists of a silicon charge coupled device (CCD) in proximity with a scintillating screen. The screen is made from a pore array having reflective pore walls and filled with CsI(Tl), emitting photons at a wavelength of 550 nm under X-ray exposure. The secondary emitted photons are light-guided by the pore walls and then detected by the CCD pixels. Detectors were fully fabricated and characterized. This concept provides good spatial resolution with negligible cross talk between adjacent pixels. The dependences of the detector efficiency on pore depth and on the coating of the pore walls are presented. Although most of the produced detectors had a detective quantum efficiency of about 25%, some detectors indicate that efficient scintillating screens can be achieved approaching the theoretical limit as set by poissonian statistics of the X-ray photons.

The two other detector designs require the formation of vertical pn junctions, i.e. in the pore walls. In one concept the secondary emitted photons are detected by photodiodes located in the pore walls. This would lead to high charge collection efficiency as the photons do not have to be guided to one end of the pore. However, high noise due to the direct detection of X-rays in the diodes is expected. The other concept is based on generation of electron-hole pairs in a semiconductor and the ‘3D’ detector, where an array of vertical electrodes is used to separate the charges via an electric field. To uniformly dope the inside of deep pores, both boron diffusion and low-pressure chemical vapor diffusion of boron-doped poly-silicon were shown to be successful techniques. This was confirmed by SIMS profiles taken through the pore wall thickness. Finally, the possibility to form individual junction in each pore was shown. The diodes were electrically characterized, demonstrating good rectifying behavior and sensitivity to light.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2005. s. viii, 69
Serie
Trita-FTE, ISSN 0284-0545 ; 2005:1
Emneord
Electrophysics, Elektrofysik
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-137 (URN)
Disputas
2005-03-07, Sal C1, KTH-Electrum, Isafjordsgatan 22, Kista, 10:15
Opponent
Veileder
Merknad
QC 20100831Tilgjengelig fra: 2005-03-03 Laget: 2005-03-03 Sist oppdatert: 2010-08-31bibliografisk kontrollert

Open Access i DiVA

Fulltekst mangler i DiVA

Andre lenker

Forlagets fulltekstScienceDirect

Personposter BETA

Linnros, Jan

Søk i DiVA

Av forfatter/redaktør
Badel, XavierLinnros, Jan
Av organisasjonen
I samme tidsskrift
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Søk utenfor DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric

doi
urn-nbn
Totalt: 439 treff
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf