Abstract: A velocity measuring system useful for monitoring repetitive bidirectional movements of a carrier, which supports workpieces in production, initially stores the values of a number of velocities representative of normal operation to establish a normal velocity range, and then compares the values of subsequent carrier velocities to the normal range. A continuing deviation from the normal range is indicative of defective actuator operation, allowing repair or replacement prior to hard failure and serious disruption of the production line.

Abstract: A particle detector includes optical fiber for conducting short wavelength radiation received from a radiation source through a chamber in which a semiconductor wafer is being processed. Light that is scattered by contaminant particles in the process chamber is sensed by an optical fiber pickup, and pulse signals are generated by a photosensing means to provide an indication of the number of particles within the process chamber.

Abstract: A real-time particle counter apparatus for monitoring contaminant particles in liquids includes a nebulizer, a drying chamber and a counter. The nebulizer provides an aerosol of droplets containing particles to the drying chamber, and the droplets are evaporated leaving solid particles to be counted and sized by the counter. Liquid is recirculated in a closed loop by pumping means that moves the liquid between the liquid source and the nebulizer. A constant air flow containing particles is provided to the counter and the apparatus is self-regulating so that no operator is required to maintain the level of liquid in the nebulizer.

Abstract: A surface scanner useful for detecting defects on the surface of a water that is being processed in a vacuum equipment employs a light beam that scans the wafer surface in an arc. The scanning light beam impinges on the wafer surface at a low angle of incidence which permits the beam to pass under photosensing elements disposed in an arcuate array substantially congruous with the arc defined by the scanning light beam. The photosensing elements are patterned close to the wafer surface to receive light scattered by defects on the wafer surface.

Abstract: A system for detection of extremely small particles in a low pressure environment or vacuum includes a vapor column in which a diffusion oil is vaporized, a saturation column in which vaporized oil is cooled and supersaturated, and means for directing a low pressure gas into the saturation column. An optical detector senses the oil droplets that grow around extremely small particles which are introduced in the saturation column by the gas and fall past the detector.

Abstract: A system for detecting contaminant particles in a liquid, such as used for processing wafers during the manufacture of integrated circuits, distinguishes non-contaminant bubbles generally found in liquids from contaminant particles. The system provides a controlled laminar fluid flow of the liquid through a pipe, and the substantially spherical bubbles in the flow path are detected by symmetrically spaced photodiodes. The irregularly shaped contaminant particles are detected, whereas the presence of bubbles are negated by the detection system by virtue of the balanced photodiode assembly.

Abstract: Photovoltaic solar cells have improved efficiency when constructed in monolithic form with two different band gap energy junctions. Solar light goes first through an upper layer containing a high band gap energy junction which absorbs the short-wavelength components of light. Then the remaining long-wavelength components are absorbed in a second active layer containing a low band gap energy junction. The cell may comprise p-n-n-p type layers.According to the invention, each low band-gap, low-voltage junction is made to have 1/2 the voltage of the high band-gap high-voltage junctions. The junctions are then connected such that the high-voltage junctions are in parallel and the series connection of low-voltage junctions is also in parallel with them. The junction voltages are invariant so the parallel connection works for any light spectrum.

Abstract: A grooved solar cell for deployment at a set angle with respect to incoming radiation has reduced contact obscuration and series resistance. A regular array of walls formed by grooves in a crystalline semiconductor substrate is exposed to incoming radiation. Metallic contacts are formed on those walls of the grooves which are not to be exposed to sunlight. The solar cell is mounted in an apparatus at a set angle with respect to incoming radiation. The array of walls is exposed to incoming radiation while the walls with metal contacts are substantially shadowed. In a preferred embodiment the grooves are formed by using orientation specific etches.

Abstract: Direct ohmic contact between the cells in an epitaxially grown cascade solar cell is obtained by means of conductive interconnects formed through grooves etched intermittently in the upper cell. The base of the upper cell is directly connected by the conductive interconnects to the emitter of the bottom cell. The conductive interconnects preferably terminate on a ledge formed in the base of the upper cell.

Abstract: A monolithic series-connected solar cell comprises a series of cells each having a mesa-like structure which is electrically interconnected from the top of each cell to a contact ledge formed in the base region of the adjoining cell. The individual cells are supported on an insulating substrate. The monolithic series-connected solar cell is fabricated from a fully formed single junction solar cell by forming a series of breaks down to an insulating substrate, forming a contact ledge in the base region on one side of the mesa defined by each break, applying a layer of insulating material along the opposite side of each mesa and forming a conductive lead between the top region of individual cells and the contact ledge of the adjoining cell.