SAMPLE Abstruct-Thisletter reports the properties of metal-nitride-Si (MNS) capacitors in which the silicon nitride layer is produced by the jet vapor deposition (JVD) technique at room temperature. Despite the room-temperature deposition, the electrical properties of these devices are far better than any previously reported MNS capacitors. Especially remarkable is the low density of interface traps (Dit < 5 X 10"/cm2 -eV near midgap). In addition, these MNS capacitors are highly resistant to damage caused by hot electrons and ionizing radiation. He + 'IH4 No NOZZLE ET vapor deposition (JVD) is a new technique [l], [2] J for preparing thin films of metals, semiconductors, dielectrics, and organics [3]-[6]. In JVD, a nozzle forms a supersonic jet of inert carrier gas that transports vapor to stationary [2] or moving [l] substrates. The vapor can be generated by thermal evaporation, sputtering, or microwave discharge inside the nozzle. The advantages of JVD compared to other techniques have been stated in [3]-[6]. In this letter we present recent results on the properties of metal-nitride-Si (MNS) capacitors in which the silicon nitride layer is produced by JVD at room temperature.Silicon nitride deposition is carried out with the coaxial nozzle jet vapor source shown in Fig. 1. Highly diluted silane from the inner nozzle and N, from the outer nozzle flow into a helium microwave discharge sustained near the outer nozzle exit. Reactive Si species and N atoms generated in the discharge are carried by the sonic He jet toward the substrate where they form silicon nitride.Substrate preparation is an important factor. The best films are deposited on Si substrates that underwent an in-situ H plasma etching (using the same jet arrangement) prior to nitride deposition to remove the native oxide and other contaminants. The deposition rate is controlled by the SiH,/He ratio and the flow rate, which critically CHAMBER WALL E W N Fig. 1. Schematic diagram of plasma-assisted jet vapor source for nitride deposition. The inner nozzle contains 20 ppm of SiH, in He at a pressure of 600 torr; the outer nozzle contains He, ", gas at a pressure of 2 torr; the deposition chamber is maintained at 0.5 torr.affects the film properties. The best films are produced at a very low deposition rate of N 15 A/min, which arises from a highly diluted SiH, gas ( -10 ppm of SiH, in He) at an inner nozzle pressure of 600 torr. The SiH, gas is further diluted by the He/N, gas coming from the outer nozzle before entering the deposition chamber, which is maintained at 2 torr. Under these deposition conditions, the nitride film exhibits an index of refraction (at h = 6328 A) of about 2.03, which is close to the value for stoichiometric Si,N,, and an etch rate of approximately 10 A/min in BOE.After the nitride deposition is complete, 2000 A of aluminum is evaporated. Aluminum gate electrodes are photolithographically defined; this is followed by back-side metallization and annealing in forming gas at 400°C for 1 h. It should be noted that no other annealin...

Measurements are presented of the reduction of signal output due to radiation damage for two types of plastic scintillator tiles used in the hadron endcap (HE) calorimeter of the CMS detector. The tiles were exposed to particles produced in proton-proton (pp) collisions at the CERN LHC with a center-of-mass energy of 13 TeV, corresponding to a delivered luminosity of 50 fb−1. The measurements are based on readout channels of the HE that were instrumented with silicon photomultipliers, and are derived using data from several sources: a laser calibration system, a movable radioactive source, as well as hadrons and muons produced in pp collisions. Results from several irradiation campaigns using 60Co sources are also discussed. The damage is presented as a function of dose rate. Within the range of these measurements, for a fixed dose the damage increases with decreasing dose rate.

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