Geneva,12 December 2001
Helsinki Institute of Physics / CMS Tracker Project
Person in charge:
Docent Jorma Tuominiemi, Program Director
Contact person:
Dr. Jaakko Härkönen
Research scientist
CERN/EP
CH-1211 Geneve
Tel: + 22 41 767 1534 / + 358 41 5109233
Fax: + 22 41 767 3600
The Helsinki Institute of Physics (HIP) is a physics research institute
that is operated jointly by the University of Helsinki, the Helsinki University
of Technology and the University of Jyväskylä. The research activity at the
institute covers an extensive range of subjects in theoretical physics and
experimental particle physics. The mandate of the institute is to carry out and
facilitate research in basic and applied physics as well as in technical
research at international accelerator laboratories. The institute is responsible
for the Finnish collaboration with CERN.
Our current activities related to Silicon detectors are focused on the device processing, as well as on the characterization of defects induced by radiation and processing. In 2001 the HIP became a member of Helsinki University of Technology Microelectronics Center (MEC). MEC provides clean room facilities and equipment for complete semiconductor processing for its member laboratories. During 2001 about 40 silicon strip detectors were processed. The experiences have been very promising: the most important electrical parameter of detectors, the leakage current, has been comparable to the values commercial manufactures are able to provide. In addition, in November 2001 the HIP silicon detector group studied the radiation hardness properties of different silicon materials at Jyväskylä University Accelerator Laboratory. The results will be submitted for publication in international scientific journals.
HIP is also operating the silicon test beam telescope (SiBT) at the CERN H2 experimental area. The telescope is used to measure high-resolution tracks of the incoming beam particles. SiBT is based on position sensitive Silicon strip detectors with a HIP built readout electronics and data acquisition system. SiBT offers a reference track measurement for the needs of the HIP/CMS detector group as well as for the other CMS research groups testing the spatial resolution and efficiency of their detectors.
At the beginning of 2002 we are planning to launch two research projects
related to Silicon detectors. Both of the projects will be funded by the
Technology Development Center of Finland and industry. The first project aims
to get deeper understanding about the physical mechanisms causing the leakage
current in silicon detectors. The project includes processing of test
structures at the premises of Microelectronics Technical Research Center of
Finland (VTT Electronics). The other partners in this project are Helsinki
University of Technology, University of Oulu, and several Finnish companies
working with silicon technology.
The other project is focused on the processing technology and
applications of <110> orientated silicon material. This crystallographic
orientation allows wet etching of deep holes or trenches with high aspect
ratio. The Finnish wafer manufacturer Okmetic Ltd has started the production of
this kind of wafers due to the demand from the MEMS industry. One possible
application of <110> silicon, the 3-dimensional particle radiation
detector, will also be studied in this project.
There are several points of convergence between our current and future
activities and the activities of the proposed R&D collaboration. In the
following we present the topics that are of special interest to us:
Device processing. The
silicon processing facilities of the Helsinki University of Technology
Microelectronics Center offers the advantage of flexibility. This might be
important especially when “non –CMOS compatible” structures are needed.
Characterization of the Silicon material quality. Process induced impurities and defects can
significantly alter the device properties. Our group has knowledge about the
characterization of silicon, especially with PCD (Photoconductivity Decay) and
SPV (Surface Photovoltage) methods.
Irradiations. Our group
has access to 15 MeV proton irradiation facilities through a joint-research
contract with the University of Jyväskylä Accelerator Laboratory. We have 28
days of beam time scheduled for the next year.
Characterization of radiation defects. In addition to the conventional characterization methods, such as DLTS
and electrical measurements, we would like to extend the defect evaluation to
the electro–optical methods, such as PCD and SPV, mentioned above. These
measurements give minority carrier recombination lifetimes or diffusion lengths
that are related to the concentration of defects. Lifetime measurements can be
carried out using different injection levels and different temperatures. This
can help to identify the trap levels or defect complexes induced by particle
radiation.
Device processing and characterization will be carried out using the facilities and equipment of the Helsinki University of Technology (HUT) Microelectronics Center (MEC) where HIP is a member laboratory. For more details see: http://www.hut.fi/Units/MEC/
Proton irradiations will be carried out at Jyväskylä University Accelerator Laboratory where HIP has a joint-research contract.
Persons to be involved into the proposed project:
|
Name |
Share oftime |
Responsibility |
|
Dr. Jaakko Härkönen |
30% |
Coordination, Silicon processing and characterization, irradiation
tests, data analysis |
|
Lic.Sc.(Tech.) Eija
Tuominen |
10% |
Irradiation tests, data analysis |
|
Dr. Kati Lassila-Perini |
10% |
Irradiation tests |
|
Dr. Saara Nummela |
20% |
Irradiation tests |
|
M.Sc. (student) Esa Tuovinen |
50% |
Silicon processing and characterization |
|
M.Sc.(Tech.) Jukka Nysten |
10% |
Irradiation tests and data analysis |