Abstract: Each sub-stage of an amplifier stage includes a resistor coupled to another resistor in an adjacent sub-stage or to a high DC voltage, the resistor and the other resistor forming part of a string of equal valued resistors; an FET having a source coupled to a cathode of a Zener diode coupled in parallel with a capacitor, a drain coupled to another sub-stage in the string, an output node of the amplifier stage, or the high DC voltage; and at least one active device coupled to a gate of the FET and coupled to the resistor for providing high impedance between a voltage on a node of the resistor and the gate of the FET and a low impedance between the at least one active device and the gate of the FET, the at least one active device coupled to both the cathode and an anode of the Zener diode.

Abstract: Each sub-stage of an amplifier stage includes a resistor coupled to another resistor in an adjacent sub-stage or to a high DC voltage, the resistor and the other resistor forming part of a string of equal valued resistors; an FET having a source coupled to a cathode of a Zener diode coupled in parallel with a capacitor, a drain coupled to another sub-stage in the string, an output node of the amplifier stage, or the high DC voltage; and at least one active device coupled to a gate of the FET and coupled to the resistor for providing high impedance between a voltage on a node of the resistor and the gate of the FET and a low impedance between the at least one active device and the gate of the FET, the at least one active device coupled to both the cathode and an anode of the Zener diode.

Abstract: An electrostatic voltmeter has an input sensing terminal, a first operational amplifier, a second operational amplifier, a first reference voltage terminal electrically connected to the non-inverting input of the second operational amplifier, a low reference voltage terminal electrically connected to the output of the second operational amplifier, and a voltage indicator, electrically connected between the low reference voltage terminal and the first reference voltage terminal.

Abstract: An ion balance monitor for simultaneous monitoring of the positive and negative ion production rates, and therefore ion concentration, by measurement of currents resulting from the presence of airborne ions as created for example by an air (gas) ionizer. Additionally it examines the ion balance by comparing the aforementioned currents. Information acquired in this way can be used in real time monitoring of the ionizer. Ion balance and production rate of ions of both polarities can be recorded by the ion monitor, regardless of the type of the ionizer. The ion monitor can provide a feedback signal needed to keep an ionizer system in balance.

Abstract: An electrostatic voltmeter has an input sensing terminal, a first operational amplifier, a second operational amplifier, a first reference voltage terminal electrically connected to the non-inverting input of the second operational amplifier, a low reference voltage terminal electrically connected to the output of the second operational amplifier, and a voltage indicator, electrically connected between the low reference voltage terminal and the first reference voltage terminal.

Abstract: A non-contacting electrostatic voltmeter (ESVM) technique and apparatus having a spacing-independent dynamic response characteristic. Using the disclosed technique, an ESVM apparatus is capable of detecting and measuring electrostatic voltages and/or fields over wide variations of sensing probe to measured surface spacing with little or no variation in the dynamic response (speed and waveform) of the reported electrostatic voltage being measured. Disclosed is a feedback circuit that provides the spacing independence of the speed of response of an electrostatic voltmeter. In particular, the method and apparatus of the invention provides an AC-type auxiliary feedback loop that provides a means for a DC-feedback electrostatic voltmeter to maintain a fixed gain and thus stable response of the DC loop over a broad range of distances between the sensing electrode and measured surface.

Abstract: A platen for electrostatic wafer clamping apparatus comprising a platen body of dielectric material and grains of electrically conductive material diffused in the dielectric material so that the platen has a relatively large electrostatic capacitance due to the diffusion of the conductive grains with the result that the platen provides an increased clamping force regardless of humidity. In accordance with another aspect of the invention, the thickness of the platen body can be decreased by an amount sufficient to maintain a constant clamping force with reduced applied voltage, to eliminate any residual voltage on the platen and to increase the speed of wafer release. The grains of electrically conductive material are present in an amount of from about 2.5 percent to about 15.0 percent of the volume of the platen body, and the grains of electrically conductive material are selected from the group consisting of carbonated transition metals, nitrified transition metals and carbonated grains.

Abstract: A platen for electrostatic wafer clamping apparatus comprising a platen body of dielectric material and grains of electrically conductive material diffused in the dielectric material so that the platen has a relatively large electrostatic capacitance due to the diffusion of the conductive grains with the result that the platen provides an increased clamping force regardless of humidity. In accordance with another aspect of the invention, the thickness of the platen body can be decreased by an amount sufficient to maintain a constant clamping force with reduced applied voltage, to eliminate any residual voltage on the platen and to increase the speed of wafer release. The grains of electrically conductive material are present in an amount of from about 2.5 percent to about 15.0 percent of the volume of the platen body, and the grains of electrically conductive material are selected from the group consisting of carbonated transition metals, nitrified transition metals and carbonated grains.

Abstract: A sensor for an electrostatic detector including an elongated vibratory element supported at a mechanical node at one end in the manner of a cantilever beam, a sensitive electrode on the vibratory element near the other end and adapted to be disposed toward an electrical charge, field or potential being measured, and a driver transducer on the vibratory element for vibrating the element in a direction to vary the capacitive coupling between the electrode and the electrical charge, field or potential being measured. An amplifier and the sensitive electrode are combined in an assembly on the vibratory element thereby providing a low impedance amplifier output which in turn allows a narrow spacing around the vibratory element to prevent entry of contaminants. The vibratory element can be provided with a structure which allows measurements with various spatial resolution characteristics.

Abstract: A sensor for an electrostatic detector comprising an elongated vibratory element supported at a mechanical node at one end in the manner of a cantilever beam, a sensitive electrode on the vibratory element near the other end and adapted to be disposed toward an electrical charge, field or potential being measured, and a driver transducer on the vibratory element for vibrating the element in a direction to vary the capacitive coupling between the electrode and the electrical charge, field or potential being measured. The driver transducer is at a location along the beam and is operated at a vibratory frequency such that a virtual mechanical node appears along the beam. This, in turn, prevents vibration of the mechanical node so that the degree of stiffness of the mechanical node does not affect the operating frequency and/or the displacement at the free end of the cantilever.

Abstract: An electrostatic force microscope wherein electrostatic force applied to the detector is determined through obtaining the field distribution on several different shaped detectors with the calculation of the voltage distribution near the detector with the Finite Element Method to direct the measurement of the absolute charge amount on surface under test so that one can define the differences between the analysis and the results from the parallel plate model. Of interest is how large the error in the charge detection occurs in conjunction with thickness change of dielectric materials to be tested. There is provided a detector with cantilever which has proper shape for the spatial resolution of 10&mgr; made out of nickel foil for an electrostatic force microscope and the electrostatic force which appeared on it has been calculated.

Abstract: A floating plate ion monitoring system and method wherein an ion collector assembly comprises an ion conducting surface and shielding surface in spaced relation, the ion conducting surface being located to receive ion impingement thereon, and wherein a potential is applied to the shielding surface which duplicates and follows the voltage appearing on the ion conducting surface. As a result, the capacitance between the ion conducting surface and the shielding surface is established electrically and independent of the physical configuration of the ion collector assembly. The foregoing is accomplished by providing a unity gain connected operational amplifier and connecting the positive input thereof to the ion conducting surface and the inverting input thereof to the shielding surface. An indicator connected to the amplifier output monitors the voltage on the ion conducting surface.

Abstract: An electrostatic force microscope for measuring electrostatic force of a sample under test including a detector comprising a cantilever arm having a tip formation at one end and located so that electrostatic force is induced at the tip due to electrostatic charge on the sample under test, an optical system for transforming bending of the cantilever arm due to electrostatic force induced at the tip into an electrical signal containing a frequency component of the electrostatic force induced at the detector tip, a source for applying bias voltage to the detector, a detector for detecting the frequency component of the electrostatic force induced at the detector tip so that a measurement of electrostatic force on the sample under test can be obtained, and an electrostatic shield operatively associated with the cantilever arm. The shield is located between the cantilever arm and the sample under test, in particular in close spaced relation to the arm.

Abstract: A high spatial resolution low noise method and apparatus for determining electrical characteristics such as the voltage density distribution or the charge density distribution of an electrophotographic medium having a surface and capable of holding electrical charge wherein a sensor is provided in close proximity to the surface, electrical charge is applied to the surface, relative movement is caused between the surface and an edge of the sensor, a substantially zero voltage difference is maintained between the sensor and the surface, there is detected a signal induced on the sensor edge in response to variation in the voltage or charge on the surface as it crosses the sensor edge, and an electrical parameter of the signal is measured to provide information on the variation of the voltage or charge on the surface to determine the voltage density distribution or the charge density distribution on the surface.

Abstract: A system and method for applying charge to a photoconductive surface wherein an electrode is spaced between the surface and a shield including applying a voltage to the electrode such that current therein is the sum of surface charging current and shield current, utilizing the shield current to obtain a signal proportional to the surface charging current and utilizing that signal to control the application of voltage to the electrode. The shield current and the sum of shield current and surface charging current flow in different directions relative to a current summing node and the signal proportional to surface charging current is obtained from the node. That signal is compared to an input control signal to control the application of voltage to the electrode. A high voltage supply has an output, a return input and a control input and variations in a signal applied to the control input cause variations in the output of the supply.

Abstract: A non-contacting electrostatic voltage follower comprising a detector electrode sensitive to electrostatic quantities such as electrostatic fields, voltages, charges and the like, a modular coupled to the electrode for modulating the capacitance coupling between the electrode and a surface bearing an electrostatic quantity to which the electrode is exposed, a detector amplifier of the current summing type having the summing input thereof connected to the detector electrode, and a high bandwidth amplifier having an input connected to the output of the detector amplifier. A probe comprises a transparent carrier element coupled to the modulator, a first conductive and transparent film on a surface of the carrier and defining the detector electrode, and a second film of conductive and transparent material on the remainder of the surface of the carrier and spaced from the first film.

Abstract: A non-contacting electrostatic voltage follower employs a vibrating capacitance detector coupled to a measured surface containing both wideband electrostatic A.C. data and D.C. potentials. A detector amplifier having an inverting input is connected to the detector, while its output is connected to the input of a high bandwidth amplifier. A first feedback path is provided from the output of the high bandwidth amplifier to the non-inverting input of the detector amplifier which provides both a signal which is equal to and follows the wideband electrostatic A.C. potentials on the measured surface, and a signal, at the vibrating capacitance modulation frequency, representative of the D.C. potential of the measured surface. A second feedback path is provided including a demodulator and integrator to monitor the first feedback path to provide a D.C.

Abstract: A non-contacting electrostatic detector comprising a detector electrode sensitive to an electrostatic quantity, a modulator coupled to the electrode for moving the electrode relative to a surface bearing the electrostatic quantity to which the electrode is exposed to produce capactive modulation of the physical capacitance beween the electrode and the surface, and an amplifier having an inverting input serving as a summing node and a non-inverting input, the electrode being connected to the inverting input and the amplifier being connected as a summing amplifier by an impedance connected between the amplifier output and the inverting input. An a.c. voltage signal having a frequency equal to the frequency of the modulator is applied to the non-inverting input of the amplifier. The amplitude and phase of the a.c.

Abstract: A sensor for an electrostatic voltmeter comprising an elongated vibratory element supported at one end in the manner of a cantilever beam, a sensitive electrode on the vibratory element near the other end and adapted to be disposed toward an electrical field or potential being measured, a driver chip on the vibratory element for vibrating the element in a direction to vary the capacitive coupling between the electrode and the electrical field or potential being measured, and an amplifier on the vibratory element in direct proximity to the sensitive electrode and having an input connected to the electrode and an output adapted for connection to the electrostatic voltmeter. The amplifier is mounted directly on the vibratory element so as to be in synchronous motion with the electrode. Preferably the electrode is mounted on one side of the vibratory element and the amplifier is mounted on the opposite side.