Western Digital Technologies, Inc.

Asml Netherlands B.v.

Alvin Jianjiang Wang

Shafa Dahandeh

Manmohan K Sharma

Patrick J Lee

Jen-Shiang Wang

Mu Feng

Jiao Liang

Khoa Xuan Bui

Chang An Wang

A method for determining measurement data of a printed pattern on a substrate. The method involves obtaining (i) images of the substrate including a printed pattern corresponding to a reference pattern, (ii) an averaged image of the images, and (iii) a composite contour based on the averaged image. Further, the composite contour is aligned with respect to a reference contour of the reference pattern and contours are extracted from the images based on both the aligned composite contour and the output of die-to-database alignment of the composite contour. Further, the method determines a plurality of pattern measurements based on the contours and the measurement data corresponding to the printed patterns based on the plurality of the pattern measurements. Further, the method determines a one or more process variations such as stochastic variation, inter-die variation, intra-die variation and/or total variation.

Method for determining stochastic variation of printed patterns

A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of data tracks. A first data track is read to generate a first read signal, the first read signal is sampled to generate first read signal samples, a first data sequence is detected based on the first read signal samples, and the first data sequence is converted into corresponding first expected samples. A second data track adjacent the first data track is read to generate a second read signal, the second read signal is sampled to generate second read signal samples, and a second data sequence is detected based on the second read signal samples and the first expected samples.

Data storage device comprising sequence detector compensating for inter-track interference

A disk drive is disclosed comprising a disk comprising a plurality of data tracks, and a head comprising a first read element and a second read element. The first read element is positioned over a first data track and the second read element is positioned over a second data track. A first analog read signal emanating from the first read element is adjusted based on a second analog read signal emanating from the second read element in order to reduce noise in the first analog read signal due to interference from the second data track.

Disk drive compensating for inter-track interference in analog read signal

A data storage device is disclosed comprising a disk comprising a plurality of data tracks, and a head comprising a first read element and a second read element. A first data track is read using the first read element to generate a first read signal, and the first read signal is sampled to generate first signal samples. A first branch metric is generated in a first trellis sequence detector when detecting a first data sequence based on one of the first signal samples. A second data track adjacent the first data track is read using the second read element to generate a second read signal, and the second read signal is sampled to generate second signal samples. A second branch metric is generated in a second trellis sequence detector when detecting a second data sequence based on one of the second signal samples and the first branch metric.

Data storage device using branch metric from adjacent track to compensate for inter-track interference

A data storage device is disclosed comprising a head actuated over a disk. A read signal from the head is sampled to generate signal samples, and the signal samples are filtered with an equalizer filter to generate equalized samples. The equalized samples are filtered with an inter-track interference (ITI) filter to generate ITI attenuated samples, and a data sequence is detected based on the ITI attenuated samples. In one embodiment, the ITI filter comprises a transfer function:1&#x2212;HPF()and in another embodiment the ITI filter comprises a transfer function:1&#x2212;LPF()where erepresents a noise sequence in the equalized samples, HPF represents a high pass filter operating on e, and LPF represents a low pass filter operating on e.

Data storage device comprising equalizer filter and inter-track interference filter

A disk drive is disclosed comprising a head actuated over a disk, and control circuitry operable to measure a transition response of the disk drive. A test pattern is written to the disk in order to write a plurality of substantially isolated magnetic transitions on the disk. The test pattern is read from the disk to generate a read signal, and the read signal is sampled to generate signal samples. A first plurality of the signal samples is extracted representing a first magnetic transition, and a second plurality of the signal samples is extracted representing a second magnetic transition. A transition response of the disk drive is measured in response to the first and second plurality of signal samples.

Disk drive measuring channel transition response by averaging isolated transitions in a read signal

A disk drive is disclosed comprising a head actuated over a disk comprising a sector including a periodic pattern and sector data. The sector is read with the head to generate a read signal which is sampled at a sampling frequency with a signal sampler to generate signal samples. The signal samples representing the periodic pattern are processed to measure a frequency induced phase error based on k&#x3b4; where k represents a signal sample index and &#x3b4; is a fraction of 2&#x3c0;. The signal samples representing the sector data are processed to generate a data phase error. The data phase error is adjusted in response to the frequency induced phase error to generate an adjusted data phase error, and the signal sampler is controlled in response to the adjusted data phase error.

Disk drive adjusting digital phase locked loop over sector data with frequency induced phase error measured over preamble

A disk drive is disclosed comprising a head actuated over a disk, the head comprising a magnetoresistive (MR) read element. An analog read signal emanating from the MR read element is amplified to generate an amplified analog read signal. The amplified analog read signal is filtered in continuous-time to extract a dc component. An amplitude of the amplified analog read signal is measured in continuous-time, and an asymmetry in the amplified analog read signal is estimated in response to the dc component and the amplitude. The amplified analog read signal is modified in response to the estimated asymmetry to generate a compensated analog read signal.

Disk drive compensating for asymmetry of magnetoresistive read element

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of data tracks. A read signal emanating from the head is sampled to generate read samples, and first log-likelihood ratios (LLRs) are generated in response to the read samples. The first LLRs are biased to generate biased LLRs, and the biased LLRs are decoded into a data sequence, wherein the biased LLRs increase an error rate of the data sequence.

Disk drive margining read channel by biasing log-likelihood ratios of an iterative decoder

A disk drive is disclosed comprising a disk, a head actuated over the disk to generate a read signal, and a trellis detector for detecting an estimated data sequence from the read signal. The trellis detector comprises a sampling device operable to sample the read signal to generate a sequence of signal sample values, and a plurality of add/compare/select (ACS) circuits each corresponding to a state in a trellis. Each ACS circuit comprises a first and second branch metric calculators for computing first and second branch metrics in response to first and second errors adjusted in response to first and second deltas that compensate for a distortion in the read signal.

Disk drive comprising a trellis detector having a read signal whitener in the ACS circuit

A disk drive is disclosed comprising a head actuated over a disk having a plurality of tracks. A pattern is read from the disk to generate a read signal, and the read signal is sampled to generate read samples. Predictable disturbing samples are generated as a function of the pattern. The predictable disturbing samples are added to the read samples to generate disturbed samples, and a data sequence is detected from the disturbed samples.

Disk drive margining read channel using predictable disturbance samples generated as a function of a written pattern

A disk drive is disclosed comprising a disk and a head actuated radially over the disk, wherein the head generates a read signal. A sampling device samples the read signal to generate a sequence of read signal samples, and an equalizer comprising a plurality of coefficients, equalizes the read signal samples to generate a sequence of equalized samples. A sequence detector detects an estimated data sequence from the equalized samples, wherein the sequence detector operates according to a target response comprising a plurality of target values. Control circuitry adapts the equalizer coefficients by computing error values in response to a difference between expected samples and the equalized samples, computing a gradient in response to a correlation of the read signal samples with the error values, and adjusting at least one of the equalizer coefficients in response to the gradient.

Disk drive adapting equalizer relative to bit error rate of sequence detector

A disk drive is disclosed comprising a disk and a head actuated radially over the disk, wherein the head generates a read signal. A sampling device samples the read signal to generate a sequence of read signal samples when reading a training data sequence recorded on the disk, and an equalizer comprising a plurality of coefficients equalizes the read signal samples to generate a sequence of equalized samples. A sequence detector detects an estimated data sequence from the equalized samples, wherein the sequence detector operates according to a target response comprising a plurality of target values. Control circuitry adapts the target values by computing error values in response to a difference between expected samples and the equalized samples, computing a gradient in response to a correlation of the training data sequence with the error values, and adjusting at least one of the target values in response to the gradient.

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Fremont, CA, United States of America

Alvin Jianjiang Wang