Panja Luukka

Radiation hardness of high resistivity magnetic Czochralski silicon detectors after gamma, neutron, and proton radiations

High resistivity magnetic Czochralski Si detectors were irradiated with /sup 60/Co gamma rays, neutrons, and protons to various doses/fluences, along with control float zone Si detectors. 1) It has been found that for gamma radiation, magnetic Czochralski Si detectors behave similarly to the high-temperature, long-time (HTLT) oxygenated float zone Si detectors. There is no space charge sign inversion and there is a buildup of positive space charges. The rate for this buildup is much higher than that for the oxygenated Si detectors and is proportional to the oxygen concentration. 2) For neutron radiation, there is little difference between magnetic Czochralski and control float zone silicon detectors. Space charge sign inversion is observed for both materials. The introduction rate of deep acceptors (beta) for magnetic Czochralski Si detectors is slightly less than that for control float zone Si detectors, and 3) for proton radiation (10 and 20 MeV), although the space charge sign inversion is also observed for magnetic Czochralski Si detectors, the 1-MeV neutron-equivalent space charge sign inversion fluence is about three times higher than that of magnetic Czochralski Si detectors irradiated with neutrons. Also, the acceptor introduction rate beta is about half of that for oxygenated Si detectors. Thus, high resistivity magnetic Czochralski Si behaves in a similar manner to the HTLT oxygenated float zone Si detectors and is even more radiation resistant to damage caused by charged particles.

Beam Test Measurements With 3D-DDTC Silicon Strip Detectors on n-Type Substrate

For the planned luminosity upgrade of the CERN LHC to the sLHC new radiation hard technologies for the tracking detectors are investigated. Corresponding to the luminosity increase, the radiation dose will be approximately a factor of ten higher than for the detectors currently installed in the LHC experiments. One option for radiation tolerant detectors are 3D silicon detectors with columnar electrodes penetrating into the silicon bulk. This article reports results of beam test measurements performed with 3D-DDTC (Double-Sided, Double Type Column) silicon strip detectors, where the columns do not pass through the detector completely. The devices were produced by IMB-CNM (Barcelona, Spain) and by FBK-irst (Trento, Italy). Important properties like space-resolved charge collection and efficiency are investigated.

Test beam results of a large area strip detector made on high resistivity Czochralski silicon

Abstract We have tested the detection performance of a strip detector processed on silicon wafer grown by magnetic Czochralski (MCZ) method. This is the first time a full size Czochralski detector has been tested in a beam, although the advantages of CZ silicon have been known before. Prior to test beam measurements, the electrical characteristics of the Czochralski silicon detectors were found to be appropriate for particle detection. Using the Helsinki Silicon Beam telescope at CERN H2 test beam, the performance of the Czochralski silicon detector was shown to be comparable with the existing silicon strip detectors.

Particle Detectors made of High Resistivity Czochralski Grown Silicon

We describe the fabrication process of fullsize silicon microstrip detectors processed on silicon wafers grown by magnetic Czochralski method. Defect analysis by DLTS spectroscopy as well as minority carrier lifetime measurements by µPCD method are presented. The electrical and detection properties of the Czochralski silicon detectors are comparable to those of leading commercial detector manufacturers. The radiation hardness of the Czochralski silicon detectors was proved to be superior to the devices made of traditional Float Zone silicon material.

Radiation Hard Silicon for Medical, Space and High Energy Physics Applications

The objective of this paper is to give an overview on how silicon particle detector would survive operational in extremely harsh radiation environment after luminosity upgrade of the CERN LHC (Large Hadron Collider). The Super-LHC would result in an integrated fluence 1×1016 p/cm2 and that is well beyond the radiation tolerance of even the most advanced semiconductor detectors fabricated by commonly adopted technologies. The Czochralski silicon (Cz-Si) has intrinsically high oxygen concentration. Therefore Cz-Si is considered as a promising material for the tracking systems in future very high luminosity colliders. The fabrication process issues of Cz-Si are discussed and the formation of thermal donors is especially emphasized. N+/p-/p+ and p+/n-/n+ detectors have been processed on magnetic Czochralski (MCz-Si) wafers. We show measurement data of AC-coupled strip detectors and single pad detectors as well as experimental results of intentional TD doping. Data of spatial homogeneity of electrical properties, full depletion voltage and leakage current, is shown and n and p-type devices are compared. Our results show that it is possible to manufacture high quality n+/p-/p+ and p+/n-/n+ particle detectors from high resistivity Czochralski silicon.

Characterization of Radiation Hard Silicon Materials

Segmented silicon detectors are widely used in modern high-energy physics (HEP) experiments due to their excellent spatial resolution and well-established manufacturing technology. However, in such experiments the detectors are exposed to high fluences of particle radiation, which causes irreversible crystallographic defects in the silicon material. Since 1990’s, considerable amount of research has gone into improving the radiation hardness of silicon detectors. One very promising approach is to use magnetic Czochralski silicon (MCz-Si) that has been found to be more radiation hard against charged hadrons than traditional Float Zone silicon material (Fz-Si) used in the current HEP applications. Other approaches include operating the devices at cryogenic temperatures and designing special detector structures such as p-type detectors or semi-3D detectors. In order to demonstrate that the developed technologies are suitable for the HEP experiments, it is necessary to extensively characterize the potentially radiation hard detectors. We have an excellent instrument for this, the Cryogenic Transient Current Technique (C-TCT) measurement setup, which is an effective research tool for studying heavily irradiated silicon detectors. With the C-TCT setup it is possible to extract the full depletion voltage, effective trapping time, electric field distribution and the sign of the space charge in the silicon bulk in the temperature range of 45-300 K. This article

Investigation of voltages and electric fields in silicon semi 3D radiation detectors using Silvaco/ATLAS simulation tool and a scanning electron microscope

The structure of silicon semi three-dimensional radiation detector is simulated on purpose to find out its electrical characteristics such as the depletion voltage and electric field. Two-dimensional simulation results are compared to voltage and electric field measurements done by a scanning electron microscope.