A device is described that enables the rapid sensing of molecules with a high degree of sensitivity and selectivity. This device is based on a depletion mode FET in which the gate electrode has been removed, certain molecular receptor species (e.g. proteins, oligonucleotides, antibodies, etc.) have been affixed, and a test solution is exposed to the gate. A counter electrode is immersed in the solution in order to establish a reference potential. Changes in the source-drain current indicate an attachment response of the system. Preliminary results are presented.

Schottky diodes with patterned overlayers of thin metal films have provided a method to measure the energy loss of high energy electrons in the metal films. The technique avoids the problems of surface contamination and electron collection which complicate measurements on freestanding films. The patterned overlayer creates a modulation in the reverse biased diode current as a beam of focused electrons is moved across the diode surface. The amplitude of the modulation has been measured with overlayers of aluminum and gold for incident electron energies of 5 to 30 keV. The results have been compared to that predicted from a Monte Carlo calculation of the inelastic and elastic scattering of the incident electrons. Significantly better agreement between experiment and simulation is observed when the screened Rutherford cross section in the Monte Carlo code is replaced by an empirical expression for the Mott scattering formula.

The subtractive patterning of fine-linewidth (sub-250-nm) tungsten absorbers for x-ray masks requires the ability to etch features with high aspect ratios and vertical sidewalls. In this letter, a reactive-ion-etching process which meets these requirements is described. The etch gases used are SF6 and H-2. It is further shown that an intermittent etch process, whereby the sample is vented to atmosphere in between etches results in an etch profile with vertical tungsten sidewalls. This interrupted etching is compared with the results from continuous etching. The straighter sidewalls in the case of the interrupted etch suggests a passivation of the sidewalls which occurs during the venting process. Results are presented to show etching of 100 nm gratings and 200 nm dot arrays. An in situ endpoint detection method developed for the reactive-ion-etching system is presented.

A process for etching fine features in tungsten (100 nm linewidth or less) to produce patterned absorbers has been developed. The pattern is first defined in a chrome etch mask on the tungsten absorber layer using e-beam lithography and s then transferred into the tungsten by reactive-ion-etching. H2 is mixed with SF6 to passivate the sidewalls of the tungsten features because SF6 alone causes severe undercutting of the features. Control of undercutting is the key challenge in reactive ion etching of tungsten. With an optimum mixture of 20% H2 and 80% SF6, plus substrate cooling to -25 degree(s)C, undercutting can be controlled for 250 nm geometries. Increased undercutting has been observed at the endpoint of the etching process, the chromium etch stop layer. This is demonstrated through a computer model. The endpoint can be controlled through laser endpoint detection. For sub 250 nm geometries, additional sidewall passivation is accomplished with an intermittent etch process, thereby allowing the etching of high aspect ratio 100 nm features in 650 nm thick tungsten layers.

Rear-surface illuminated charge-coupled devices (CCD’s) are typically insensitive to radiation whose depth of penetration is less than 1000 Å. This is due to the presence of immobile charges either in the rear-surface native oxide or at the native oxide/semiconductor interface. These fixed charges channel signal charge away from the front-surface confinement minima. The result is a loss of detective quantum efficiency (DQE), which is defined as the number of signal charges actually collected divided by the number produced. The CCD can be sensitized to shallow-penetrating radiation through the use of ion implantation techniques. To model the sensitization process, four factors must be accounted for. They are: the extent of the rear-surface depletion created by the fixed charge, Debye length spreading of the mobile charge background in the semiconductor, the position of the implant maximum, and the gradient of the active implant charge before the implant maximum is reached. By judicious manipulation of these factors DQE’s as high as 20% (uncorrected for UV reflection loss) have been obtained at 1216 Å.

Theory, engineering design, fabrication, and experimental test of the first completely monolithic grating amplifier realized in silicon are described. Experimental results are presented for frequencies between 0.1 and 2.0 GHz at 300 K for the device, referred to as the solid state space harmonic amplifier structure. Electronic gain is about 1.5 dB/mm with a cold circuit loss of 4.6 dB/mm for the 200-μm-long interaction region device.

This paper describes the development of backside illuminated, deep-depletion charge coupled devices (CCD's) optimized for imaging in the ultraviolet. A model is presented to describe the UV detection process at the CCD backside, and the factors controlling the UV quantum efficiency. A 32 x 32-pixel area imager was obtained with excellent operating characteristics, such as high transport efficiency and low readout rwise. By appropriate treatments of the CCD backside, a quantum efficiency of 20% at 1216 Å was obtained on the best devices. Good resolution was obtained in the visible and UV regions of the spectrum.

Dislocations extending through channel regions of NMOSFETs with submicron gate lengths have been observed. Additionally, arrays of dislocations in the field regions of IC’s have also been observed and found to be generating from the corners of the first n+ region during subsequent high temperature process.

The effects of low energy ionizing irradiation on MOS structures, with doses typical of those encountered in x-ray lithography, were studied in capacitors and transistors. The capacitor studies indicated the irradiations induced a slow trapping instability and an increase in surface state density. This surface state density increase was partially annealed at 450C in N2 after 1/2 hour. Transistor t...