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A Silicon-On-Insulator (SOI) Technology is suitable for vertex detectors for high energy physics experiments since complex functions can be fabricated on the SOI wafer with a small amount of material thanks to the monolithic structure. We developed a new sensor processing scheme “PIXOR(PIXel OR)” for pixel detectors using a LAPIS 0.20 μ m SOI process. An analog signal from each pixelated sensor is divided into two dimensional directions, and 2 n signal channels from a small n by n pixel matrix are ORed as n column and n row channels, then the signals are processed by a readout circuit in each small matrix. This PIXOR scheme reduces the number of readout channels and avoids a deterioration of intrinsic position resolution due to large circuit area, that was a common issue for monolithic detectors. This feature allows high resolution, low occupancy and on-sensor signal processing at the same time. We present the successful results of the PIXOR readout scheme using a first prototype.

We have been developing active pixel sensors based on silicon-on-insulator technology for future X-ray astronomy missions. Recently we fabricated the new prototype named “XRPIX2”, and investigated its spectroscopic performance. For comparison and evaluation of different chip designs, XRPIX2 consists of 3 pixel types: Small Pixel, Large Pixel 1, and Large Pixel 2. In Small Pixel, we found that the gains of the 68% pixels are within 1.4% of the mean value, and the energy resolution is 656 eV (FWHM) for 8 keV X-rays, which is the best spectroscopic performance in our development. The pixel pitch of Large Pixel 1 and Large Pixel 2 is twice as large as that of Small Pixel. Charge sharing events are successfully reduced for Large Pixel 1. Moreover Large Pixel 2 has multiple nodes for charge collection in a pixel. We confirmed that the multi-nodes structure is effective to increase charge collection efficiency.

We have been developing a monolithic active pixel sensor with the silicon-on-insulator (SOI) CMOS technology for use in future X-ray astronomical satellite missions. This sensor is called XRPIX. Our objective is to replace the X-ray CCD, which is currently the standard detector in the field, with the developed XRPIX, which offers high coincidence time resolution (~ 50 ns), superior hit-position readout time (~ 10 μs), and wide bandpass (0.5-40 keV), in addition to having comparable performance in terms of imaging spectroscopy. In our previous study, we built a prototype sensor called XRPIX1 and confirmed its basic X-ray imaging spectroscopy performance in a mode that read out the entire area (all pixels). The next step is to realize a high-speed, intelligent readout for X-ray detection. XRPIX1 comprises a trigger circuit for each pixel, so as to detect an X-ray photon injection; this system is capable of direct access to selected pixels to read out the signal amplitude. We describe the design of the trigger circuitry system and report on the first resolved X-ray spectra obtained in the trigger-driven readout mode.

We have been developing monolithic active pixel sensors with 0.2 μm Silicon-On-Insulator (SOI) CMOS technology, called SOIPIX, for high-speed wide-band X-ray imaging spectroscopy on future astronomical satellites. In this work, we investigate a revised chip (XRPIX1b) for soft X-rays used in frontside illumination. The Al Kα line at 1.5 keV is successfully detected and energy resolution of 188 eV (FWHM) is achieved from a single pixel at this energy. The responsivity is improved to 6 μV/electron and the readout noise is 18 electrons rms. Data from 3 ×3 pixels irradiated with 6.4 keV (Fe Kα) X-rays demonstrates that the circuitry crosstalk between adjacent pixels is less than 0.5%.

We have been developing an active pixel sensor for X-ray astronomy. In this paper, we report on the design and the characterizationof the recently-developed device named XRPIX1-FZ.We applied the high-resistivitySiwafer(∼7 kΩ cm) to the sensor layer for a thick depletion layer. The chemical-mechanical polishing, which we applied to smooth the rough backside of the Si wafer, successfully reduced the dark current. We used the single-pixel readout mode and achievedthe energy resolution of 260eVinFWHMat8keV.Moreover, we developed the 3 × 3pixel readout mode for the evaluation of split events and confirmed the full depletion of 250 μm thick at thereverse-biasvoltageof30 V

We have been developing a monolithic active pixel sensor with the 0.2 μm Silicon-On-Insulator (SOI) CMOS technology, called SOIPIX, for the wide-band X-ray imaging spectroscopy on future astronomical satellites. SOIPIX includes a thin CMOS-readout-array layer and a thick high-resistivity Si-sensor layer stacked vertically on a single chip. This arrangement allows for fast and intelligent readout circuitries on-chip, providing advantages over the charge-coupled device (CCD). We have designed and built a new SOIPIX prototype XRPIX1 for X-ray detection. XRPIX1 implements a correlated double sampling (CDS) readout circuit in each pixel to suppress the reset noise. We obtained an energy resolution of full width at half maximum of 1.2 keV (5.4%) at 22 keV with a chip having a 147 μm sensor depletion at a back bias of 100 V cooled to -50°C. Moreover, XRPIX1 offers intra-pixel hit trigger (timing) and two-dimensional hit-pattern (position) outputs. We also confirmed the trigger capability by irradiating a single pixel with laser light.

With an increase in the operation frequency of complimentary metal oxide semiconductor (CMOS) circuits, a radio-frequency system-on-a-chip (RF-SOC) that integrates GHz-RF and large-scale digital circuits becomes a key device for wireless systems and high-speed networks. To develop high-performance RF-SOCs, high quality voltage controlled oscillators (VCOs) are required as local oscillators or clock generators, which operate in noisy environments suffering from crosstalk noise generated by digital circuits. A 0.25 µm CMOS test chip for a new differential-input VCO and a conventional single-input VCO was designed with on-chip CMOS logic noise sources and substrate noise detectors. The jitter and phase noise of the VCOs were measured to investigate the effect of substrate crosstalk noise. We confirmed that the differential-input VCO is robust to low-frequency noise in comparison with a conventional single-input VCO.

In order to investigate the p-side strip isolation, position sensitivity and charge collection of type-inverted double-sided silicon microstrip detectors, signal amplitude and charge sharing of adjacent strips were measured by using a laser test stand, following the irradiation with a flux of 3.8×1013 /cm2 of 12 GeV protons. The irradiated detectors indicated high bulk resistivity, which results in maintaining a position sensitivity of the ohmic contact side even below the full depletion voltage. This fact suggests a possibility of operation of a double-sided detector whose full depletion voltage becomes higher than its breakdown limit because of a radiation damage.

A double-sided, double metal, AC coupled readout silicon microstrip sensor (DDSMS) has been developed for the SVX-II, the upgrade vertex detector for CDF. Key issue in the development is to achieve sufficient radiation hardness for survival in the radiation environment of several kGy/yr. The required high-voltage capability and the reduction of the readout capacitance of the double-metal side were critical design goals. Detailed design methods to radiation-hard silicon sensors are discussed.

A large area (63.6 mm/spl times/64 mm) n-on-n silicon strip detector was fabricated, implementing various p-stop structures in the n-side. The detectors were characterized in laboratory and in beam tests. The inter-strip capacitance showed features in which the individual p-stop structure had the longest tail toward saturation. The beam tests showed other p-stop structures collected more charge in the mid-strip region than the individual p-stop structure. In addition, there was a source which lost or spread charge and induced noise where the over-depletion was insufficient.

We have developed a monolithic pixel detector with the silicon-on-insulator (SOI) pixel CMOS technology to use as radiation monitor, called RADPIX. The RADPIX intends to identify the type of radiation (α, β, γ, muon, etc.) by differences in hit pattern. The sensor is DC-coupled to the input of the pixel circuit so the leakage current I leak of a few pA for 40 µm × 40 µm at room temperature must be sunk by the pixel circuit for long time exposure. The RADPIX has the individual leakage compensation circuit. In addition to a digital output, the analog signal also can be read by using the comparator output as a store signal to latch the analog signal for the tracking accuracy enhancement. The prototype chip consists of 32 × 32 pixels with the pixel size of 40 µm × 40 µm (∼1 mm square sensitive area). We report the design and the result of the basic evaluation test.

We have been developing a monolithic active pixel sensor with the silicon-on-insulator (SOI) CMOS technology for use in future X-ray astronomical satellite mission. Our objective is to replace the X-ray Charge Coupled Device (CCD), which is the standard detector in the field, by offering high coincidence time resolution (∼ 50 ns), superior hit-position readout time (∼ 10 μs), and wider bandpass (0.5 – 40 keV) in addition to having comparable performances in imaging spectroscopy. In order to realize this detector, we have developed prototype detectors, called “XRPIX” series. XRPIX contains comparator circuit in each pixel to detect an X-ray photon injection; it offers intra-pixel hit trigger (timing) and two-dimensional hit-pattern (position) outputs. Therefore, XRPIX is capable of direct access to selected pixels to read out the signal amplitude. In our previous study, we evaluated its basic performance and obtained the X-ray spectra by this system. The next step is improvement in spectroscopic performance. Then, we designed a new prototype, called “XRPIX3”, which has charge sensitive amplifier (CSA) in each pixel. The pixel circuit with CSA works good. It is 3.4 times higher gain as compared with normal pixel circuit. Furthermore, XRPIX3 resolved Mn-K α and Mn-K β successfully for the first time in our series. The readout noise is 33 e- rms and the energy resolution is about 300 eV FWHM at 5.9 keV. In this paper, we report on the design and test results of this new device.

We have investigated the micro-discharge (micro-breakdown) phenomenon which is potentially a serious problem in operating in a high radiation environment. Numerical calculation of field strength for the model structure of the microstrip sensor gives us a quantitative understanding of each different cause of micro-discharge. The structure of the microstrip sensor can be optimized through this field calculation for suppressing the micro-discharge. We propose a new strip structure to suppress the micro-discharge.

We have examined experimentally some existing ideas for improving the radiation hardness of silicon microstrip sensors. We confirm that the extended electrode and the deep implant-strip proposed on the basis of simulation studies works effectively to suppress micro-discharge as well as junction breakdown of the bias or guard ring. For an integrated coupling capacitor a double layer structure of SiO 2 and Si 3 N 4 provides better radiation hardness than that of single SiO 2 coupling in our design conditions. The onset voltage of the micro-discharge on the bias/guard ring has been studied for an extended electrode and a floating guard ring.

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. >

We report on the evaluation test of our novel pixel sensor named "XRPIX1-FZ" which is developed for the future X-ray astronomy mission. The mean gain of XRPIX1-FZ is 3.3 µV/e. and the dispersion of the gain among the pixels is 1% in the standard deviation. We confirmed the energy resolution of 260 eV in FWHM at 8 keV. We achieved the full depletion (250 µm) at 30 V back bias voltage.

A full-size prototype microstrip sensor for the silicon tracker of the SDC detector to be used at the Superconducting Super Collider has been fabricated at Hamamatsu Photonics. The sensor is double-sided, using an AC-coupled readout with 50 μm pitch strips. The sensor size is 3.4 × 6.0 cm 2 . Polycrystalline silicon is used as a bias feeding resistor on both surfaces. Each ohmic strip is isolated by a p + blocking line. The detailed requirements for the silicon tracker and the corresponding specifications as well as how to achieve them are discussed. The static performances of this prototype sensor are presented.

Microdischarge at the edges of strips in AC-coupled silicon strip sensors has been investigated. A steep increase in the leakage current (breakdown) and a sudden onset of burst noise were observed at a low reverse-bias voltage when the bias potential was across the AC-coupling capacitor. This can be explained by the occurrence of microdischarges along the edges of strips. These discharges have been confirmed by observing IR light emission. A calculation of the field strength at the strip edge suggests that a fringe field of the external electrode generates the microdischarge at the strip edge when the bias voltage is 50–80 V. This is consistent with our observations. We discuss a design for AC-coupled sensors that eliminates this discharge problem.

We have been developing a monolithic active pixel sensor with the Silicon-On-Insulator (SOI) CMOS technology, called SOIPIX, for future X-ray astronomical satellite missions. The goal of SOIPIX is to replace the X-ray CCD, which is the standard detector in the field, by offering superior time resolution (∼10 µs) and wider bandpass (0.5 keV – 40 keV) in addition to having comparable performances in imaging spectroscopy. In the previous work, we built a SOIPIX prototype, XRPIX1, and confirmed the basic X-ray performance of imaging spectroscopy in a mode reading out the whole area (all pixels). The next step is to realize a high-speed and intelligent readout for X-ray detection. XRPIX1 contains trigger circuit in each pixel to detect an X-ray photon and is capable of direct access to the local pixels to read out the signal amplitude. We report on the design and development of a trigger-driven readout system with XRPIX1. We present the first resolved X-ray spectra of Cu+Mo and Am-241 obtained in the trigger-driven mode.

We have been developing a novel X-ray astronomy detector combined with a CMOS readout circuit on a monolithic chip using the SOI CMOS technology. As a part of the development, we have fabricated a prototype of an analog-to-digital converter (ADC) component aiming for building it into the detector itself. We used the OKI 0.2 µm CMOS fully depleted Silicon-On-Insulator process. The prototype ADC consists of a pre-amplifier and two delta-sigma (ΔΣ) modulators. The two modulators process a series of analog input signal alternately to improve the readout speed (∼100 kHz), and output the digital bit-stream signal. An external Field Programmable Gate Array works as a decimation filter and converts the bit-stream signal into a 12-bit digital signal. We evaluated the prototype ADC and obtained the first results as follows: the power consumption of 40 mW, the equivalent input noise of ∼80 µV rms, and the integral non-linearity of less than 0.8%.

We have been developing a monolithic active pixel sensor with the 0.2 μm Silicon-On-Insulator (SOI) CMOS technology, i.e. SOIPIX, for the X-ray imaging spectroscopy on future astronomical satellites. SOIPIX includes a thin CMOS readout layer and a thick high-resistivity Si-sensor layer vertically on a single chip, which would provide advantages in capabilities of direct and flexible readout circuitries over charge-coupled device (CCD). We have built INTPIX2/3 (2008/2009) and XRPIX1(2010). We successfully confirmed the capability of X-ray imaging and spectroscopy in a photon-counting mode by irradiating INTPIX2/3 with monochromatic X-rays. To reduce the readout noise, we designed and built XRPIX1, which has a correlated double sampling (CDS) readout circuit in each pixel to suppress the reset noise. We obtained an energy resolution of FWHM ∼1.5 keV(7%)@22 keV with XRPIX1 cooled at 50 degree. Moreover, XRPIX1 offers intra-pixel hit trigger and one-dimensional hit-pattern outputs. We also confirmed the trigger capability by irradiating a single pixel of XRPIX1 with laser light.

A beam test was executed to evaluate the behavior of the first prototype radiation-hard double-sided silicon microstrip sensor for the SDC silicon tracking system. Pions of 4 GeV/c in a test bcamline at KEK illuminated three planes of detectors. Thc signals wcrc amplified, shaped, and discriminated with TEKZ bipolar analog LSI's, and the on-off levels were sampled at l0MHz clock with CMOS digiwl LSI's, asynchronously with beam triggers. The detectors were rotated in null and 1 .O Tesla magnetic fields. The efficiencies were found to be 98-9996. The position resolutions were 12.5pm. where the multi-strip hit fraction was 30-40%. There was no essential difference in the performance of the pand the n-sides. The multi-strip hit fraction showed a clear rotation and magnetic-field dependence. From the angles where the fractions were minimum in the 1T magnetic field, the Hall mobilities of the electrons and holes were obtained to be 1391k43 (clcctrons) and 325f30 (holes) cm2/Vs.

A full-size, double-sided, AC coupling sensor for the SDC central tracker was fabricated. The bias feeding resistor for each strip on both surfaces was implemented by a poly-Si line. The resistance was well controlled within a design value which is good enough to feed uniform bias to each strip. The ohmic-contact strip isolation was attained by inserting a p/sup +/ channel between n/sup +/ strips. The readout capacitance was minimized by making a narrow strip on the p/sup +/ side and by inserting a wide isolation p/sup +/ channel in the n/sup +/ strip side. The capacitance is measured to be 0.8 pF/cm on the p/sup +/ strip side and 1.13 pF/cm on the n/sup +/ strip side. The junction edge breakdown voltage has been pushed up to more than 150 V by an Al strip narrower than the implanted strip width. >

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/N/sub 4/, in combination with the surface passivation of SiO/sub 2/ or Si/sub 3/N/sub 4/. 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 0/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. >

A n,-bulk AC-coupling double-sided silicon strip detector, designed to have a high tolerance to radiation, was characterized with fast binary readout electronics to the pion beams. The detector was beamtested before and after the proton irradiation. The proton irradiation was non-uniform and to increase the damage the detector was heated to accelerate the anti-annealing. The effective radiation level was about 1/spl times/10/sup 14/ p/cm/sup 2/ The detector was characterized by varying two parameters: bias voltage of the detector and the threshold of the discriminator of the binary readout electronics. The irradiated detector has clearly shown the effect of bulk inversion, the move of p-n junction from the p-side to the n-side, both in the efficiency variation with a fixed threshold and in the median pulse height distribution, as a function of bias voltage. In the irradiated region, collected charge in the n-side has shown the characteristic /spl radic/V dependence of the depletion depth. The binary system was proved to be efficient well below the full depletion voltage in the p-n junction side. The detector, being irradiated highly non-uniformly, the bulk changing from nearly intrinsic to the damage of about 1/spl times/10/sup 14/ p/cm/sup 2/ within the detector, worked without any noticeable failures.

Activity controllable noise source and arrayed substrate voltage detectors use a 0.25-/spl mu/m, 2.5-V CMOS technology and enable substrate noise measurements with controlled logic density/activity distributions. These circuits are used for exploring effects of power-supply parasitic components on substrate noise generation in practical large-scale CMOS digital circuits. Spatially distributed parasitic impedances on power-supply and return wirings cause the noise generation locally, and moreover, screen the effect of noise attenuation by parasitic capacitances of logic elements working as charge reservoirs.

A double-sided silicon strip detector with a radiation-tolerant design was fabricated and characterized in a sequence of beam tests at KEK using 4 GeV/ c pions. The detectors were combined with newly designed, fast, lower power, bipolar amplifier-shaper-discriminator chips and CMOS digital pipeline chips to record hit-no hit signals in the strips. Efficiencies, noise occupancies, and spatial resolutions were measured before and after the proton irradiation at an equivalent fluence of 1 × 10 14 p/cm 2 , depending on angle of track incidence and strip-pitches. The median pulse height distribution, derived from the threshold scans of the efficiency, allowed to extract the response of the detector. A 1 T magnetic field enabled us to determine the Hall mobilities of electrons and holes.

Precision tracking and vertex reconstruction play a crucial role in heavy flavor physics at CDF, in reconstructing the charm and beauty decay vertices in beauty and top events. A significant upgrade to the CDF detector, including a new silicon tracker, will support an extensive physics program with the high luminosity provided by the Main Injector accelerator upgrade. The specifications and design considerations for this new silicon tracker/vertex detector are discussed.