Abstract: A levelized simulation system includes a means for storing a model of a logic system to be simulated. The logic system has a plurality of levels of logic which are synchronously clocked. A processing system including an arithmetic logic unit sequentially tests each element of said logic system, one level of logic at a time, thus each logic element in the first level is tested with the results there stored in a state memory, after which the logic elements of the second level of the logic system are tested and so on. During each test a comparison is made to determine whether there is a defect in the logic design.

Abstract: An electrical discharge is applied to a wafer mounted in a wafer holder. The wafer includes at least one conducting region covered by an insulating layer. The discharge causes a conductive channel from the conductive region through the insulating layer. The conductive channel provides a relatively low impedance path suitable for conducting away electrons which are injected into the region during processing steps such as electron beam exposure.

Abstract: An electrical discharge is applied to a wafer mounted in a wafer holder. The wafer includes at least one conducting region covered by an insulating layer. The discharge causes a conductive channel from the conductive region through the insulating layer. The conductive channel provides a relatively low impedance path suitable for conducting away electrons which are injected into the region during processing steps such as electron beam exposure.

Abstract: A table positioning apparatus suitable for use in an electron beam exposure system. A movable table holds a wafer or other work piece. The table is driven by a motor in response to a motor drive signal to position the table at different locations. An optical position measuring transducer is located in fixed relation to the table to establish a reference position for the table in a local region. The transducer provides a position signal as a function of the table position in the local region. An amplifier is provided which is responsive to the position signal to produce a servo signal. A motor drive circuit provides the motor drive signal for driving the motor in response to the servo signal so that the table is driven to the reference position. At the reference position, a reset signal is provided to reset interferometers in both X and Y axes.