Displacement measuring grating interferometer: a review

Hu, Pengcheng; Chang, Di; Tan, Jiubin; Yang, Ruitao; Yang, Hongxing; Fu, Haijin

doi:10.1631/fitee.1800708

Cited by 70 publications

(29 citation statements)

References 160 publications

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“…A Michelsontype interferometer can also be formed by a heterodyne GI, as shown in Figure 19. 55 A polarized laser beam with two frequencies f 1 and f 2 is produced by a dual-frequency laser. The light is split into two beams by a NPBS, one beam is detected by the PD r to form a reference signal, the other beam is divided into two parts by a polarized beam splitter (PBS) and enters the reference grating and the measuring grating respectively.…”

Section: Stage Position Measurementmentioning

confidence: 99%

Mechanical system and dynamic control in photolithography for nanoscale fabrication: A critical review

Song

Chen

Huo³

et al. 2021

Int Journal of Mech Sys Dyn

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As one of the most advanced and precise equipment in the world, a photolithography scanner is able to fabricate nanometer-scale devices on a chip. To realize such a small dimension, the optical system is the fundamental, but the mechanical system often becomes the bottleneck. In the photolithography, the exposure is a dynamic process. The accuracy and precision of the movement are determined by the mechanical system, which is even more difficult to control compared with the optical system. In the mechanical system, there are four crucial components: the reticle and wafer stages, the linear motor, the metrology system, and the control system. They work together to secure the reticle and substrate locating at the correct position, which determines the overlay and alignment performance in the lithography. In this paper, the principles of these components are reviewed, and the development history of the mechanical system is introduced.

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Section: Stage Position Measurementmentioning

confidence: 99%

Mechanical system and dynamic control in photolithography for nanoscale fabrication: A critical review

Song

Chen

Huo³

et al. 2021

Int Journal of Mech Sys Dyn

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“…Only those beams that forms quadrature signals are shown. However there are other diffraction directions provided by diffraction grating Equation (1) and not used in the optical system in which diffraction efficiency should be minimized. The beam splitting on reference and measurement scales is carried out in accordance with the grating equation…”

Section: Optical Conceptmentioning

confidence: 99%

“…Linear displacement sensors with fixed reading head determine the current coordinate and displacement direction of an object connected with the measurement scale [1][2][3]. Optical interferential sensors show the highest resolution and accuracy for linear displacement measurements.…”

Section: Introductionmentioning

confidence: 99%

Phase Imbalance Optimization in Interference Linear Displacement Sensor with Surface Gratings

Одиноков

Shishova

Kovalev

et al. 2020

Sensors

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In interferential linear displacement sensors, accurate information about the position of the reading head is calculated out of a pair of quadrature (sine and cosine) signals. In double grating interference schemes, diffraction gratings combine the function of beam splitters and phase retardation devices. Specifically, the reference diffraction grating is located in the reading head and regulates the phase shifts in diffraction orders. Measurement diffraction grating moves along with the object and provides correspondence to the displacement coordinate. To stabilize the phase imbalance in the output quadrature signals of the sensor, we propose to calculate and optimize the parameters of these gratings, based not only on the energetic analysis, but along with phase relationships in diffraction orders. The optimization method is based on rigorous coupled-wave analysis simulation of the phase shifts of light in diffraction orders in the optical system. The phase properties of the reference diffraction grating in the interferential sensor are studied. It is confirmed that the possibility of quadrature modulation depends on parameters of static reference scale. The implemented optimization criteria are formulated in accordance with the signal generation process in the optical branch. Phase imbalance and amplification coefficients are derived from Heydemann elliptic correction and expressed through the diffraction efficiencies and phase retardations of the reference scale. The phase imbalance of the obtained quadrature signals is estimated in ellipticity correction terms depending on the uncertainties of influencing parameters.

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“…Due to their high accuracy, robustness against environmental variances, relatively low cost, and compactness, grating encoders now hold more than 75% market share among various precision positioning solutions. Depending on the measurement method, there are two trends of grating encoders; one is single axis ultra-high precision and the other is multi-axis [1][2][3][4][5][6]. For high precision applications, the diffraction beam interferometry principle is utilized.…”

Section: Introductionmentioning

confidence: 99%

An FPGA Platform for Next-Generation Grating Encoders

Han

et al. 2020

Sensors

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Among various nanometer-level displacement measurement methods, grating interferometry-based linear encoders are widely used due to their high robustness, relatively low cost, and compactness. One trend of grating encoders is multi-axis measurement capability for simultaneous precision positioning and small order error motion measurement. However, due to both lack of suitable hardware data processing platform and of a real-time displacement calculation system, meeting the requirements of real-time data processing while maintaining the nanometer order resolutions on all these axes is a challenge. To solve above-mentioned problem, in this paper we introduce a design and experimental validation of a field programmable gate array (FPGA)-cored real-time data processing platform for grating encoders. This platform includes the following functions. First, a front-end photodetector and I/V conversion analog circuit are used to realize basic analog signal filtering, while an eight-channel parallel, 16-bit precision, 200 kSPS maximum acquisition rate Analog-to-digital (ADC) is used to obtain digital signals that are easy to process. Then, an FPGA-based digital signal processing platform is implemented, which can calculate the displacement values corresponding to the phase subdivision signals in parallel and in real time at high speed. Finally, the displacement result is transferred by USB2.0 to the PC in real time through an Universal Asynchronous Receiver/Transmitter (UART) serial port to form a complete real-time displacement calculation system. The experimental results show that the system achieves real-time data processing and displacement result display while meeting the high accuracy of traditional offline data solution methods, which demonstrates the industrial potential and practicality of our absolute two-dimensional grating scale displacement measurement system.

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Displacement measuring grating interferometer: a review

Cited by 70 publications

References 160 publications

Mechanical system and dynamic control in photolithography for nanoscale fabrication: A critical review

Mechanical system and dynamic control in photolithography for nanoscale fabrication: A critical review

Phase Imbalance Optimization in Interference Linear Displacement Sensor with Surface Gratings

An FPGA Platform for Next-Generation Grating Encoders

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