Hitachi, Ltd.

Yukichi Ueno

Masahide Okumura

Yoshio Sakitani

Yasushi Nakaizumi

Atsushi Shibata

Teiji Katsuta

Toshiaki Nakata

Kenichiro Takahasi

Kenitiro Takahashi

An A/D converter comprises a D/A conversion circuit, a sample-holding circuit which samples and holds the output signal of the D/A conversion circuit, a substraction circuit which performs subtraction for the output signal of the D/A conversion circuit and the output signal of the sample-holding circuit, a subtracting-amplifying circuit which performs subtraction for the output signal of the substraction circuit and the input analog signal and amplifies the result of subtraction, a switch circuit which blocks the input analog signal to the subtracting-amplifying circuit, and an A/D conversion circuit which performs A/D conversion selectively for the input analog signal or the output signal of the subtracting-amplifying circuit.

High-accuracy A/D converter

In a communication network in which a main station and several I/O systems are connected by a closed-loop communication line, the communication line includes a data channel and a clock pulse channel extending in parallel with the data channel. Predetermined data bit lengths are allotted to the individual I/O systems. A train of clock pulses, the number of which is equal to the sum of the data bit lengths alloted to the I/O systems, is supplied from the main station to the I/O systems, and data arranged in the order of reception by the I/O systems are transmitted from the main station to the I/O systems in synchronism with the clock pulses. In each of a number of I/O systems, the clock pulses, corresponding to the number of data bits allotted to the particular station, is counted to fetch the data supplied while the clock pulses are being counted. At the same time, the I/O system sends out data generated therein toward the main station while the clock pulses are being counted. In the other period of time, data and clock pulses supplied to that I/O system are transferred intact to the I/O system in the next stage.

Method and apparatus for communication control in loop communication

In an ion implantation system wherein an ion beam is scanned by deflection means in a predetermined direction on substrates placed on a disc rotating at a constant speed, to implant the substrates with ions; ion beam detectors are arranged in correspondence with a plurality of places of the substrate before the ion implantation. When the ion beam is scanned, sums of outputs of the respective ion beam detectors in the plurality of scanning positions are evaluated, and correction operations are executed so that they may become constant values. The scanning rate of the ion beam by the deflection means is controlled according to the corrections. Thus, when the ion beam is actually implanted into the substrate, the density of the ion beam becomes uniform.

Beam scanning control device for ion implantation system

A method and an apparatus for testing a mask by an electron beam are disclosed in which the electron beam probe is first incident upon a predetermined point on a mask pattern of a photomask used to fabricate a semiconductor integrated circuit, the mask pattern is scanned by the electron beam probe from the predetermined point in a direction, the scanning operation is stopped when the electron beam probe reaches an edge of the mask pattern, the position of the edge or the distance between the predetermined point and the edge is determined by the number of pulse required to deflect the electron beam probe by a desired amount, and the position or distance thus determined is compared with the design data of the mask pattern to examine the dimensions of the mask pattern.

Electron beam testing method and apparatus of mask

Electric pulses are counted, and are converted into an electric signal proportional to the number of the counted pulses. An electron beam for irradiating a sample is deflected in response to the electric signal. The counting can be voluntarily stopped with a switch.

Apparatus for selecting the field of view of a sample

A field emission electron gun according to this invention comprises a cathode for emitting electrons, an anode, a high voltage source which applies a high voltage between the cathode and the anode in order to cause emission of electrons from the cathode, a reference voltage source, voltage control means for controlling and stabilizing the output voltage of the high voltage source in response to an output voltage of the reference voltage source, means for detecting the value of an emission current from the cathode, means for delivering as an output a signal corresponding to the difference between the detected value and a desired value, and means for applying the output signal to the reference voltage source through a switch. The reference voltage source includes means which, when the switch is in the closed state, controls the output voltage of the reference voltage source in response to the difference output signal, and means which, when the switch is in the open state, continues to hold the output voltage value of the reference voltage source immediately before the opening of the switch as it is. The electron gun of this invention accordingly conducts when the switch is in the closed state, a constant current operation which makes constant the emission current from the cathode, and conducts when the switch is in the open state, a constant voltage operation which makes constant the voltage applied between the cathode and the anode.

Field emision electron gun with controlled power supply

An electron producing apparatus of the field emission type wherein instantaneous values of an emitted current are sequentially measured to store a relative minimum value of the emitted current which is obtained in such a manner that one instantaneous value which is stored is then replaced by another instantaneous value which is even smaller in magnitude than the previously stored one, and at the same time the instantaneous values are sequentially compared with the stored relative minimum value so that the electron producing apparatus is deenergized when an instantaneous value assumes a certain magnitude relative to the stored relative minimum value.

Growing community of inventors

Katsuta, Japan

Yukichi Ueno