L. Andricek

Strip detector design for ATLAS and HERA-B using two-dimensional device simulation

Abstract Irradiation scenarios were simulated in order to evaluate different technology and design options for silicon strip detectors exposed to a high luminosity environment. Two-dimensional process and device simulations were performed to get an insight into the device behaviour. The boundary condition of the free oxide regions between the strips was evaluated thoroughly to obtain correct field distributions. Using these results the formation of electron accumulation layers on the surface of the p-side and the depletion voltage dependence on the strip geometry can be explained. We investigated the “blocking implant” and the “spray implant” techniques as promising candidates for the n-side isolation of irradiated detectors. The main drawback of the “blocking implanted” devices is the increase of the electric field with increasing oxide charges. This implies the danger of impact ionization in irradiated devices. A “spray implanted” isolation layer leads to the highest electric field in the non-irradiated state which has the advantage of a better testability. Small gaps between strips as used in charge division readout reduce electric fields and leakage currents.

Processing of ultra-thin silicon sensors for future e/sup +/e/sup -/ linear collider experiments

The e/sup +/e/sup -/ linear collider physics program sets highly demanding requirements on the accurate determination of charged particle trajectories close to the interaction point. A new generation of DEPFET active pixel sensors with 25 /spl mu/m pixel size is currently being developed to meet the requirements in the point measurement resolution and multiple track separation. To minimize the influence of the multiple scattering on the impact parameter resolution, the sensors have to be made as thin as possible. The paper presents a technology based on direct wafer bonding and deep anisotropic etching for the production of ultra thin fully depleted sensors with electrically active back side. PiN diodes with 50 /spl mu/m thickness have been produced in this way and the results show the feasibility of this approach. The technology is useful for the production of any kind of thin sensors with active back side (strip detectors, pad detectors etc). An integrated support frame outside the sensitive area allows for safe handling and mounting of the thin devices.

A DEPFET Based Beam Telescope With Submicron Precision Capability

For the detection of secondary vertices of long lived particles containing bottom and charm quarks at the International Linear Collider (ILC), a DEPFET pixel detector is one of the technologically favored options. In a DEPFET sensor a MOSFET pixel detector is integrated on a sidewards depleted silicon bulk sensor, thus combining the advantages of a fully depleted silicon sensor with in-pixel amplification. DEPFET pixel matrices have been characterized in a high energy particle beam. Since the DEPFET is a very high precision device, given its large S/N (> 100) and small pixel size (36 × 22 ¿m2), a DEPFET based pixel telescope consisting of 5 DEPFETs has been developed. The uncertainty on the predicted position for a device under test (DUT) positioned inside the telescope was found to be 1.4 ¿m with the existing device, due to the limited performance of two of the five DEPFET planes. A DEPFET telescope built of 5 modules equivalent to the best plane presented here, would have a track extrapolation error as low as 0.65 ¿m at the DUT plane.

New DEPMOS applications.

Abstract Several detector applications for the DEPMOS transistor as on-chip amplifier are introduced. First the principle of the DEPMOS transistor is reviewed. Then the design of a silicon drift chamber (SDC) with integrated voltage divider and DEPMOS readout is described, and a first experimental result is presented. Furthermore another two new DEPMOS applications are introduced: a fully depleted pn-CCD with DEPMOS readout and a device for multiple nondestructive readout, which will lead to a distinct reduction of random noise.

DEPFET Active Pixel Detectors for a Future Linear

The DEPFET collaboration develops highly granular, ultra-transparent active pixel detectors for high-performance vertex reconstruction at future collider experiments. The characterization of detector prototypes has proven that the key principle, the integration of a first amplification stage in a detector-grade sensor material, can provide a comfortable signal to noise ratio of over 40 for a sensor thickness of 50-75 μm. ASICs have been designed and produced to operate a DEPFET pixel detector with the required read-out speed. A complete detector concept is being developed, including solutions for mechanical support, cooling, and services. In this paper, the status of the DEPFET R & D project is reviewed in the light of the requirements of the vertex detector at a future linear e+e- collider.

e^{+}e^{-}

Abstract This R&D activity is focused on the development of new modules for the upgrade of the ATLAS pixel system at the High Luminosity LHC (HL-LHC). The performance after irradiation of n-in-p pixel sensors of different active thicknesses is studied, together with an investigation of a novel interconnection technique offered by the Fraunhofer Institute EMFT in Munich, the Solid–Liquid-InterDiffusion (SLID), which is an alternative to the standard solder bump-bonding. The pixel modules are based on thin n-in-p sensors, with an active thickness of 75 μ m or 150 μ m , produced at the MPI Semiconductor Laboratory (MPI HLL) and on 100 μ m thick sensors with active edges, fabricated at VTT, Finland. Hit efficiencies are derived from beam test data for thin devices irradiated up to a fluence of 4 × 10 15 n eq / cm 2 . For the active edge devices, the charge collection properties of the edge pixels before irradiation are discussed in detail, with respect to the inner ones, using measurements with radioactive sources. Beyond the active edge sensors, an additional ingredient needed to design four side buttable modules is the possibility of moving the wire bonding area from the chip surface facing the sensor to the backside, avoiding the implementation of the cantilever extruding beyond the sensor area. The feasibility of this process is under investigation with the FE-I3 SLID modules, where Inter Chip Vias are etched, employing an EMFT technology, with a cross section of 3 μ m × 10 μ m , at the positions of the original wire bonding pads.

Collider

Abstract Strip detectors covering radiation hardness and large-scale production ability are developed and produced for the ATLAS experiment at the Large Hadron Collider (LHC) at CERN (Switzerland). Capacitively coupled p+n detectors (p-type strips on n-type substrate) were developed with implanted bias resistors in order to simplify the detector processing addressing the requirements of large-scale production. The detectors were irradiated with 24 GeV protons up to 3×10 14 cm −2 in order to simulate a 10 years operation scenario at LHC. The presented static and signal measurements demonstrate the function of the device concept before and after irradiation.

Thin n-in-p pixel sensors and the SLID-ICV vertical integration technology for the ATLAS upgrade at the HL-LHC

The combined Detector-Amplifier structure DEPFET (Depleted P-channel FET) is a promising new building block for large area silicon detector devices, e.g. in X-ray astronomy and high energy physics. The DEPFET structure combines excellent energy resolution, high speed readout and low power consumption with the attractive features of random accessibility of pixels and on-demand readout. In addition, it features all advantages of a sideways depleted device in terms of fill factor and quantum efficiency. Finally, the newly introduced combination of a DEPFET structure and a silicon drift diode (SDD) like drift ring structure to form a so-called macropixel device allows for large flexibility in terms of pixel size. Presently, focal plane instrumentation for X-ray imaging spectroscopy based on DEPFET arrays is being developed for a variety of space experiments with very different requirements. The next European X-ray Observatory XEUS is going to have a wide field imager covering the full FOV, which consists of a large-area DEPFET array. The concept for the French-Italian X-ray Astronomy mission SIMBOL-X includes a focal plane array based on DEPFET macropixels, and, finally, the MIXS (Mercury Imaging X-ray Spectrometer) instrument on the European Mercury exploration mission BepiColombo also contains two DEPFET macropixel based focal plane arrays. While for XEUS and SIMBOL-X excellent energy resolution and quantum efficiency in the low energy range are mandatory, radiation hardness is imperative for MIXS. A first production of DEPFET prototype arrays showed very promising results. More sophisticated prototype devices for SIMBOL-X and XEUS with a large sensitive area as well as flight grade devices for the MIXS instrument have been produced at the MPI semiconductor laboratory in Munich/Germany. The strategies to meet the respective requirements by an appropriate design of the focal plane instrumentation are shown as well as first results of the new production.

Design and test of radiation hard p'n silicon strip detectors for the ATLAS SCT

One of the X-ray imaging detectors in development for the European XFEL (X-ray Free Electron Laser) is the DSSC (DEPFET Sensor with Signal Compression). The DSSC sensor array will have a format of 1024 × 1024 pixels with a pixel size in the order of 200 µm. It is optimized for the detection of low-energy X-ray photons and designed to operate at frame rates up to 4.5 MHz with a dynamic range of several thousand photons per pixel and frame and single photon resolution at small photon numbers. The DSSC systems core component is an active pixel sensor based on the DEPFET (DEpleted P-channel Field Effect Transistor) structure. A DEPFET is an integrated detector-amplifier combining internal amplification, full sensitivity over the whole bulk thickness, analog data storage, readout on demand, low serial noise, and absence of reset noise. For the DSSC-adaptation of the DEPFET principle the new feature of signal compression has been added, i.e. the device has a high gain at small signals and a reduced gain at large signals. With this strongly non-linear response the DSSC-DEPFET provides the required high charge handling capacity with simultaneous single photon resolution for low-energy X-rays. This paper presents the concept of the DSSC-DEPFET. Its functionality is demonstrated by measurements of a first series of prototypes.

DEPFET based focal plane instrumentation for X-ray imaging spectroscopy in space

We present the results of the characterization of silicon pixel modules employing n-in-p planar sensors with an active thickness of 150 μm, produced at MPP/HLL, and 100–200 μm thin active edge sensor devices, produced at VTT in Finland. These thin sensors are designed as candidates for the ATLAS pixel detector upgrade to be operated at the HL-LHC, as they ensure radiation hardness at high fluences. They are interconnected to the ATLAS FE-I3 and FE-I4 read-out chips. Moreover, the n-in-p technology only requires a single side processing and thereby it is a cost-effective alternative to the n-in-n pixel technology presently employed in the LHC experiments. High precision beam test measurements of the hit efficiency have been performed on these devices both at the CERN SpS and at DESY, Hamburg. We studied the behavior of these sensors at different bias voltages and different beam incident angles up to the maximum one expected for the new Insertable B-Layer of ATLAS and for HL-LHC detectors. Results obtained with 150 μm thin sensors, assembled with the new ATLAS FE-I4 chip and irradiated up to a fluence of 4 × 1015 neq/cm2, show that they are excellent candidates for larger radii of the silicon pixel tracker in the upgrade of the ATLAS detector at HL-LHC. In addition, the active edge technology of the VTT devices maximizes the active area of the sensor and reduces the material budget to suit the requirements for the innermost layers. The edge pixel performance of VTT modules has been investigated at beam test experiments and the analysis after irradiation up to a fluence of 5 × 1015 neq/cm2 has been performed using radioactive sources in the laboratory.