Kabushiki Kaisha Yaskawa Denki

Masamichi Inenaga

Yuji Arinaga

Shinichi Katsuda

Koji Suzuki

Takayuki Imanaka

A wafer pre-alignment apparatus according to this invention includes a wafer rotating member, a rotation detecting member, a light emitting member for emitting light toward the periphery of the wafer, a COD linear sensor linearly arranged and signal processing member for detecting the edge position of the wafer to acquire at least one of an orientation flat position, notch position and center position of the wafer on the basis of the edge position detected, and further includes an up-down counter for converting a signal received from the rotation detecting member into rotating position information, a measured angle setting register for storing the rotation position information when the wafer rotating member rotates by an interval angle and a comparator for comparing a set value in the measured angle setting register and a counted value in the up-down counter.

Wafer pre-alignment apparatus and method

An absolute encoder comprising a first memory operable to store a first absolute value signal produced every constant time period, the absolute value signal representing an absolute value position. A second memory stores a second absolute value signal produced in a previous time period. A comparing/calculating section compares the first absolute value and the second absolute value and produce a difference amount. A dividing process section divides the difference amount in an equal rate within a producing time period of said first absolute value signal. An interpolated absolute value signal producing section reads the second absolute value signal and adds the difference amount in a stepwise manner.

Absolute encoder and absolute value signal generation method

A prealignment sensor comprising a frame fixed to a base and having a U-shape when viewed from its side. A light source is attached to a lower part of the flame. A convex lens is attached to a lower part of an inside of the frame by which diffused light of the light source is transformed into parallel light. A lens holder is provided for fixing the convex lens to the frame. An optical receiver is attached to an upper part of an inside of the frame by which the parallel light is received and is transformed into an electrical signal. A signal processing circuit is attached to the frame by which the electric signal is transformed into a desired displacement magnitude. The frame is formed of aluminum subjected to sulfuric-acid hard alumite treatment and then to steam sealing.

Techniques for wafer prealignment and sensing edge position

A wafer prealignment apparatus comprising a CCD linear sensor and a wafer prealignment method which facilitate the sensing of wafer presence, improvement in precision of position sensing, and edge sensing adapted to the material of the wafer even of the material is transparent or not. A photodiode () is provided in a vicinity of the first pixel from the center shaft of the wafer rotation means of a CCD linear sensor () to detect a wafer () on the basis of the luminous energy value. The time from the issuance of a measurement command to the sensor () to that of an ROG signal for transmitting the detection timing of the sensor () is measured to correct the angular error of a measurement position due to the rotation during this measurement. For sensing an edge position of the wafer (), the scan start point of the sensor () is set on the opposite side of the center shaft of the wafer rotation means. When the wafer is transparent a sense signal is binarized to set its change point as the edge position. When the wafer is not transparent, information on a position lastly sensed as an edge is judged to be correct so that a particle may not be misrecognized as the edge.

Techniques for wafer prealignment and sensing edge positions

An absolute encoder that can generate an absolute value signal by performing simple operation processing. Phase signals &phgr; to &phgr; are represented by j-bit digital signals, a signal b provided by dividing the phase signal &phgr; by 2 (where K is an integer) is subtracted from a phase difference signal &phgr; &equals;c, an absolute value signal A &equals;f of the number of pitches (a a ) with a signal of the high-order K bits of the signal provided by subtracting the signal from &phgr; as high-order bits and &phgr; as low-order bits, subsequently a signal g provided by dividing the phase signal A &equals;f by 2 (where K is an integer) is subtracted from a phase difference signal &phgr; &equals;h, an absolute value signal A &equals;k of the number of pitches (a &minus;a ) with a signal of the high-order K bits of the signal provided by subtracting the signal from &phgr; as high-order bits and f as low-order bits, and the process is executed in order, whereby a longer-pitch absolute value signal is generated and signals are processed in order from the shorter-pitch signals to the longer-pitch signals, whereby the condition under which the pitch number cannot be determined is eliminated, and a large allowance of a phase error between slits can be taken. An error of a phase difference signal at the high-speed scale rotation time can also be corrected and adjusted by PLL.

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Fukuoka, Japan

Masamichi Inenaga