AC-coupled Silicon Microstrip Research Articles

Charge collection efficiency study of silicon microstrip sensors

The charge collection efficiencies (CCEs) of various AC-coupled single-sided silicon microstrip sensors were measured to find an optimal sensor design for different readout methods. A 820 nm wavelength pulsed laser was used as a light generation source to study the responses of the prototype microstrip sensors. Five different microstrip sensors of two types (A and B) were designed for this purpose and were fabricated on high resistivity and n-type silicon wafers. The readout pads in types A and B were located inside and outside the guard ring surrounding the active sensor area, respectively. The sensors at an operating voltage of 80 V were irradiated by using a pulsed laser, producing ∼22000 electron-hole pairs per pulse. The signals, ADC counts, were measured by moving the sensors while maintaining the laser in a fixed position. The CCEs for 10 different microstrip sensors were calculated from the maximum and the minimum ADC counts in each designed microstrip sensor. This study showed that the hit-position dependences of the signals and the CCEs for the three different readout methods were well evaluated by using a pulsed laser without using charged particles from accelerators.

Fabrication of AC-coupled double-sided silicon strip sensor

The AC-coupled double-sided silicon microstrip sensors are designed and 14 masks are used to produce prototype strip sensors. The biasing resistors are made of p-doped polysilicons and the coupling capacitors are built by separating implanted strips and readout strips by a thin oxide layer. The p-stops in the atoll patterns are introduced to disrupt an electron accumulation layer at the Si–SiO2 interface on the ohmic side. The junction side has a double metal structure using two metal layers separated from each other by a thick insulator layer. The strip sensors are fabricated on a 5-in., high resistivity, 〈100〉-orientation, and 380μm thick n-type double-sided polished silicon wafer. The prototype sensor with an area of 2.8×2.8cm2 consists of 256(512) readout channels with a strip pitch of 100(50)μm. The leakage currents and the bulk capacitances as a function of the reverse bias voltage are measured to understand the fabrication process of the prototype sensors. The signal to noise ratios are measured by using a 90Sr radioactive source in order to evaluate performance of the sensors. The design of the AC-coupled double-sided silicon strip sensor and its various components are described, and measurements of the electric characteristics and the signal to noise ratio are presented.

Qualification of a large number of double-sided silicon microstrip sensors for the ALICE Inner Tracking System

Delivery of more than 2000 AC-coupled double-sided silicon microstrip sensors, designed to equip the two outermost layers of the ALICE Inner Tracking System, has been recently completed by three manufactures. This represents the largest production of this type of sensors undertaken so far. Sensor testing and quality control has been performed at INFN Trieste. A careful optimization of the testing procedures has allowed performing a thorough qualification of the large number of sensors without making use of automated device-handling equipment. The paper presents an overview of the test procedures and results.

What can be learned from the BABAR Silicon Vertex Tracker running experience

The Silicon Vertex Tracker (SVT) of the BABAR experiment at SLAC is a crucial tool to measure with precision the decay position of B mesons produced in the PEP-II electron–positron collisions. It is structured in five layers made of double-sided, AC coupled silicon microstrip sensors. In this paper, a review of some of the technical solutions chosen in the detector design phase is presented. In particular, we focus here on those elements which turned out to be sources of problems during the installation and the first few years of operation; the solutions adopted to solve the problems are presented together with recommendations and proposals for alternate future designs.

Radiation damage studies for the B aB ar Silicon Vertex Tracker

The Silicon Vertex Tracker of the B aB ar experiment is a five-layer, double-sided AC-coupled silicon microstrip detector operating on the PEP-II storage ring at the Stanford Linear Accelerator Center. After more than four years of running, the silicon sensors and the front-end electronics in the inner layer have absorbed radiation doses up to 2 Mrad. In this paper we present results from radiation hardness tests and discuss the implications of the absorbed radiation dose on the Silicon Vertex Tracker lifetime.

Lessons learned from the BaBar Silicon Vertex Tracker

The Silicon Vertex Tracker (SVT) of the BABAR experiment at the PEP-II asymmetric B factory consists of a five-layer double sided, AC coupled silicon microstrip detector. It represents a key element to measure with precision the decay position of B mesons, satisfying the severe constraints imposed by the accelerator design, in terms of geometry of the interaction region and conditions of operation. In the following paper, a critical review of the SVT general design and performance is made, with special attention to those details of the design and the assembly procedure that are considered a source of possible problems given the experience accumulated during the construction, the commissioning and the first 5 years of operation.

The BaBar Silicon Vertex Tracker: performance and radiation damage studies

The BaBar Silicon Vertex Tracker is a five layers, double sided AC-coupled silicon microstrip detector operating on the PEP-II storage ring at the Stanford Linear Accelerator Center. The performance of the SVT after 4 years of running is described. Results from radiation hardness tests are presented and the implications of the absorbed radiation dose on the SVT lifetime are discussed.

Performance of the BABAR silicon vertex tracker

The Silicon Vertex Tracker (SVT) of the BABAR experiment at the PEP-II asymmetric B factory is a five layer double sided, AC coupled silicon microstrip detector. It represents the crucial element to precisely measure the decay position of B mesons . The SVT architecture is shown and its performances, like hit resolutions and efficiencies, are described. Radiation issues are discussed and the alignment procedure for the SVT is described. As an example for the physics performance the B lifetime measurement, including B vertex reconstruction, is shown.

The BaBar silicon-vertex tracker: performance, running experience, and radiation-damage studies

The silicon-vertex tracker (SVT) for the BaBar Experiment at the PEP-H Asymmetric B Factory at Stanford Linear Accelerator Center (SLAC), is a five-layer double-sided ac-coupled silicon-microstrip detector. It is a crucial element for the precise measurement of the decay position of B mesons, satisfying the severe constraints imposed by the accelerator design, in terms of geometry of the interaction region and conditions of operation. In the following paper, the SVT performance is described. Radiation issues are discussed and the results of different tests aimed to study the decrease in the SVT performance due to radiation damage are presented. The alignment procedure is described, and a few BaBar physics results are presented as examples of the SVT capabilities to reconstruct decay vertices with good resolution and efficiency.

The BaBar silicon vertex tracker, performance and running experience

The Silicon Vertex Tracker (SVT) of the BaBar experiment at the PEP-II asymmetric B factory is a five-layer double-sided, AC-coupled silicon microstrip detector. It represents the crucial element to precisely measure the decay position of B mesons and extract time-dependent CP asymmetries. The SVT architecture is shown and its performance is described, with emphasis on hit resolutions and efficiencies.

Development of a fabrication technology for double-sided AC-coupled silicon microstrip detectors

We report on the development of a fabrication technology for double-sided, AC-coupled silicon microstrip detectors for tracking applications. Two batches of detectors with good electrical figures and a low defect rate were successfully manufactured at IRST Laboratory. The processing techniques and the experimental results obtained from these detector prototypes are presented and discussed.

Physical modeling of silicon microstrip detectors: influence of the electrode geometry on critical electric fields

In this paper, a computer-based analysis of AC-coupled silicon microstrip detectors is presented. The study aims at investigating the main geometrical parameters responsible for potentially critical effects, such as early micro-discharges and breakdown phenomena. The adoption of CAD tools allows for evaluating the actual field distribution within the device, and makes it possible to identify critical regions. The adoption of overhanging metal strips is shown to have a positive impact on the electric field distribution, reducing corner effects and thus minimizing breakdown risks.

Feasibility study for double-sided silicon microstrip detector fabrication at IRST

Abstract This paper is concerned with the preliminary results of a technological study aimed at the development of a fabrication process for double-sided AC-coupled silicon microstrip detectors. The approach adopted for the fabrication of both single-sided and double-sided detectors is presented, and the results from electrical tests performed on detectors and test structures are reported and discussed. Good electrical characteristics as well as an acceptable number of process-related defects have been obtained for these prototype detectors, thus demonstrating the feasibility of fabricating such devices at the IRST facility.

The CLEO II.V silicon vertex detector

A description of the new silicon tracker installed in the CLEO interaction region is given. This device consists of three layers of double-sided AC-coupled silicon microstrip detectors arranged in an octagonal array. The wafers are readout by 416 CAMEX64/JAMEX64 VLSI amplifier chips. A description of the data acquisition and monitoring systems developed to read out the SVX is provided. A summary of performance and some results are presented.

Proton irradiation on AC-coupled silicon microstrip detectors

To test the radiation tolerance of full-size detectors, four large-area AC-coupled single-sided silicon microstrip detectors were fabricated. The detectors had a size of 6 cm/spl times/3.4 cm and were made out of a 300 /spl mu/m thick, high-resistivity, n-type silicon, simulating the p-side of the double-sided silicon microstrip detectors being developed. The AC coupling layer had either a single layer of SiO/sub 2/ or double layers of SiO/sub 2/ and Si/sub 3/N4. In combination with the surface passivation of SiO/sub 2/ or Si/sub 3/N4. The detectors were irradiated at room temperature by 500 MeV protons at TRIUMF to a fluence of 5.7/spl times/10/sup 13/ protons/cm/sup 2/, promptly stored at O/spl deg/C after irradiation, and periodically measured over the following year. The full depletion voltages showed a substantial annealing and a gradual anti-annealing. The result was compared with the predictions of existing damage parameterization. Time variation of other characteristics, such as leakage current, interstrip and coupling capacitances, and strip-edge microdischarges was also followed. >

Signal-to-noise in silicon microstrip detectors with binary readout

We report the results of a beam test at KEK using double-sided AC-coupled silicon microstrip detectors with binary readout, i.e., a readout where the signals are discriminated in the front-end electronics and only the hit location as kept. For strip pitch between 50/spl mu/ and 200/spl mu/, we determine the efficiency and the noise background as function of threshold setting. This allows us to reconstruct the Landau pulse height spectrum and determine the signal/noise ratio. In addition, the threshold/noise ratio necessary for operation with low occupancy is determined. >

Double-sided double-metal AC-coupled silicon microstrip detectors

Novel silicon microstrip detectors, which combine double side operation, on-chip coupling capacitors and two levels of metallization have been developed, manufactured and tested. This approach aims at very low mass system assemblies, particularly important for applications in vertex detection at LEP and at future B-factories. Devices were integrated on 100 mm diameter silicon wafers on which several dielectrics for AC coupling were tested. A SiO2Si3N4 double dielectric layer, etched between strips, performed best with respect to leakage current, breakdown voltage and oxide integrity. In order to minimize stray capacitance between strips in the 2 metal layers, an extremely thick (5.2 μm) intermetal dielectric layer was used. A special photolithographic and etching process which guarantees good step coverage was developed, resulting in tapered vias.Static measurements were carried out on detectors of various dimensions. Leakage current, depletion voltage and capacitive effects from cross-coupling between metal 1 and metal 2 were measured. In particular, the breakdown characteristics of the coupling capacitor formed by the implanted strips and the metal 1 strips were investigated for several insulators. With the SiO2Si3N4 double dielectric layer, a pinhole density of the order of 1% was obtained for some of the detectors, with leakage currents of around 100 nA/cm2. The connectivity between metal 1 and metal 2 layers was found to be excellent. The dynamic response of the detectors was studied using the VIKING front-end readout chip.The results show that these complex double-sided chips, which are required for next generation detectors, are reaching a state of maturity.

Study of 18-cm long single-sided AC-coupled silicon microstrip detectors

The SSC GEM silicon Central Tracker design incorporated 18-cm long single-sided AC-coupled silicon microstrip ladders. Compared to the 12-cm long ladders considered in the preliminary stages of the tracker design, the 18-cm long ladders have the advantage of reduced cost, channel count and overall power consumption, and led to a simplified tracker assembly. However, such long ships also present the challenge of maintaining satisfactory performance. The increased capacitance and series resistance contribute to lower signal-to-noise ratios, longer time walk, higher power consumption per channel and increased probability of crosstalk to neighboring channels. In this paper, an accurate method to calculate the geometric capacitance of the AC-coupled microstrips is presented and the calculated results are compared with measurements, SPICE simulations are performed to predict the noise, the extent of interstrip capacitive coupling and the dispersion of the detector signal due to the finite series resistance of the metal strips and the long length of the detector. The influence of the preamplifier current and the shaping time on the signal and noise levels is also presented. The study concludes that the 18-cm long ladders can successfully satisfy the performance goals of the GEM silicon Central Tracker.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Improved process of fabricating AC-coupled silicon micro-strip sensors

A single-sided silicon sensor with capacitors coupling and polysilicon bias resistors has been designed and fabricated. A proposed process with ONO (Oxide-Nitride-Oxide) replacing the usual SiO2 layer as the dielectric of coupling capacitor, in conjunction with a reordering of sequence for layer formations, is to produce sensors with self-moisture-protection and free from the effect of pin holes. A comparison of presented data of IV, CV and RV measurements for the sensors with ONO and with SiO2 dielectrics revealed that the ONO processes could lead to an excellent voltage-handling capability of the coupling capacitor. One sensor has been successfully tested twice in the beam at CERN in the past two years, yielding an S/N ratio of 20 and an efficiency above 95%, also demonstrating its excellent stability with respect to lengthy exposure to atmosphere.

Analysis of capacitance measurements on silicon microstrip detectors

We present an analysis of the total strip capacitance of double-sided, AC-coupled silicon microstrip detectors. We evaluate the radiation hardness and the noise contribution of different strip geometries. We comment on a serious failure mode. >