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CN-121977472-A - Morphology displacement measurement system and method based on sweep frequency laser interference

CN121977472ACN 121977472 ACN121977472 ACN 121977472ACN-121977472-A

Abstract

The invention discloses a morphology displacement measurement system and method based on sweep frequency laser interference. The continuous laser emitted by the sweep frequency light source is divided into two paths by the coupler, wherein one path is used as reference light and enters the reference arm, and the other path is used as measuring light and enters the measuring arm, and the continuous laser is collimated by the collimator and then vertically emitted to the blazed grating I. The measuring light is dispersed and corrected through the blazed grating I and the blazed grating II so as to vertically irradiate the measuring light to the surface of the target to be measured, and after the measuring light irradiates the target to be measured, the measuring light returns to the coupler along the original light path, is interfered with the reference light to obtain an interference light signal, and is converted into a digital electric signal through the photoelectric detector and the data acquisition module, and the digital electric signal is subjected to time-frequency analysis so as to demodulate the morphology information corresponding to different positions. The invention breaks through the limitation that the traditional interferometry can only carry out point measurement, realizes line scanning and greatly improves the morphology measurement speed.

Inventors

  • LEI XIAOHUA
  • CHENG XIAOJUN
  • ZHANG PENG
  • LIU XIANMING

Assignees

  • 重庆大学

Dates

Publication Date
20260505
Application Date
20260119

Claims (9)

  1. 1. The morphology displacement measurement system based on sweep frequency laser interference is characterized by comprising a sweep frequency light source (1), a coupler (2), a reference arm (3), a measurement arm (4), a collimator (5), a blazed grating I (6), a blazed grating II (7), a photoelectric detector and a data acquisition module (9); The continuous laser emitted by the sweep frequency light source (1) enters the coupler (2), and is divided into two paths in the coupler (2), wherein one path is used as reference light and enters the reference arm (3), and the other path is used as measuring light and enters the measuring arm (4); The measuring arm (4) is connected with the collimator (5); the measuring light enters a collimator (5) through a measuring arm (4), the collimator (5) is used for collimation, and then the collimated measuring light is vertically emitted to a blazed grating I (6); the blazed grating I (6) is used for dispersing the vertically incident continuous measurement light, so that the continuous measurement light is separated into a plurality of different-frequency dispersion lights, and then the plurality of different-frequency dispersion lights are irradiated to different positions on the blazed grating II (7); The blazed grating II (7) is used for correcting the angle of the scattered light and vertically radiating the scattered light with a plurality of different frequencies to the surface of the target (8) to be measured, and the target (8) to be measured is arranged under the blazed grating II (7); the dispersion light is reflected after being irradiated to a target (8) to be detected, returns to the coupler (2) along an original light path, and interferes with reference light positioned on the reference arm (3) to obtain an interference light signal; the photoelectric detector is respectively connected with the coupler (2) and the data acquisition module (9); the photoelectric detector is used for converting the interference optical signal into an analog electric signal and transmitting the analog electric signal to the data acquisition module (9); The data acquisition module (9) is used for converting the analog electric signals into digital electric signals, performing time-frequency analysis on the digital electric signals and demodulating morphology information corresponding to different positions.
  2. 2. A topography displacement measurement system based on swept laser interferometry according to claim 1, wherein the swept light source (1) is adapted to emit light of different frequencies at different times.
  3. 3. The morphology displacement measurement system based on sweep laser interference according to claim 1, wherein the coupler (2) is provided with four ports, namely a port I, a port II, a port III and a port IV, which are respectively connected with a sweep light source (1), a measurement arm (4), a reference arm (3) and a photoelectric detector; continuous laser emitted by the sweep frequency light source (1) enters the coupler (2) from the port I; in the coupler (2), based on a preset proportion, dividing continuous laser into two paths, wherein one path is output from a port III and used as reference light, and the other path is output from a port II and used as measuring light; The measuring light returned from the object (8) to be measured reenters the coupler (2) from the port II, reaches the port III to interfere with the reference light, and then transmits the obtained interference light signal to the photoelectric detector through the port IV.
  4. 4. The topography displacement measurement system based on sweep laser interference of claim 1, wherein the blazed grating II (7) has the same structure as the blazed grating I (6).
  5. 5. The system for measuring the topography displacement based on the swept laser interferometry according to claim 1, wherein the object (8) to be measured comprises a semiconductor micro-nano device and an integrated circuit device.
  6. 6. A method of a topography displacement measurement system based on swept laser interferometry according to any one of claims 1 to 5, comprising the steps of: s1, building a morphology measurement system, wherein the morphology measurement system comprises a sweep frequency light source (1), a coupler (2), a reference arm (3), a measurement arm (4), a collimator (5), a blazed grating I (6), a blazed grating II (7), a photoelectric detector and a data acquisition module (9); s2, placing an object (8) to be detected under the blazed grating II (7); s3, turning on a sweep frequency light source (1), emitting continuous laser through the sweep frequency light source (1), and inputting the continuous laser to a coupler (2); the continuous laser emitted at different moments has different frequencies; S4, dividing the continuous laser into two paths by using a coupler (2), wherein one path is used as reference light and enters a reference arm (3), and the other path is used as measuring light and enters a measuring arm (4) and is vertically shot to a blazed grating I (6) after being collimated by a collimator (5); S5, based on the characteristic that continuous laser has different frequencies, the blazed grating I (6) disperses continuous measurement light into a plurality of pieces of dispersed light with different frequencies, and irradiates the dispersed light with different frequencies to different positions on the blazed grating II (7); s6, enabling the dispersion light to vertically irradiate to the surface of the target (8) to be detected through the blazed grating II (7), and after the dispersion light irradiates to the target (8) to be detected, returning the dispersion light to the coupler (2) along an original light path, and interfering the dispersion light with the reference light (3) positioned on the reference arm to obtain an interference light signal; S7, transmitting the interference optical signals to a photoelectric detector, converting the interference optical signals into analog electric signals through the photoelectric detector, transmitting the analog electric signals to a data acquisition module (9), converting the analog electric signals into digital electric signals by the data acquisition module (9), and carrying out time-frequency analysis on the digital electric signals to demodulate the morphology information corresponding to different positions.
  7. 7. The system for measuring the topography displacement based on the swept laser interferometry according to claim 1, wherein in the step S4), the measuring light has a delay time relative to the reference light Delay time of The calculation formula of (2) is as follows: (3) (4) (5) wherein: Is the speed of light; Is that Continuously measuring the displacement of the light irradiated on the target to be measured; the vertical distance between the blazed grating II and the target to be measured is set; is the optical path difference generated by blazed grating I and blazed grating II; At present for the object to be measured Morphology change amounts of the moment and the last adjacent moment; The vertical distance between the blazed surfaces of the blazed gratings I and II is the same; The slit distance between the blazed grating I and the blazed grating II.
  8. 8. The system for measuring the topography displacement based on the swept laser interferometry according to claim 1, wherein in the step S6), the intensity of the interference light signal is The calculation formula of (2) is as follows: (8) (9) wherein: the frequency of the light output by the sweep frequency light source is the frequency of the light; is the initial phase of the reference light; To measure the initial phase of the light; Is the initial phase difference of the reference light and the measurement light.
  9. 9. The system for measuring the topography displacement based on the swept laser interferometry according to claim 1, wherein in the step S7), the digital electrical signal is subjected to time-frequency analysis to obtain a complete instantaneous frequency curve Instantaneous frequency curve The functional expression of (2) is: (10) Integrating the instantaneous frequency curve, and recovering the phase information to obtain the displacement corresponding to each moment : (11) Wherein: An initial position for irradiating the measuring light on the target to be measured; based on the displacement corresponding to each moment Obtaining the shape change quantity : (12) Morphology change according to time and wavelength information Mapping to the position of line scanning, and obtaining the morphology change information of each position point.

Description

Morphology displacement measurement system and method based on sweep frequency laser interference Technical Field The invention relates to the technical field of morphology measurement, in particular to a morphology displacement measurement system and method based on sweep frequency laser interference. Background In the field of semiconductor manufacturing, integrated circuits as a core technology directly determine the performance, power consumption and cost of electronic devices. The integrated circuit is manufactured by a plurality of process flows including photoetching, etching, film deposition and the like, and the process flows all need to detect the surface morphology of the semiconductor material. The feature detection is a key link for ensuring the performance and quality of the integrated circuit, the measurement accuracy of the feature detection is directly related to the qualification rate of the chip, and the detection requirement on the surface feature reaches the nanometer or even sub-nanometer level along with the continuous miniaturization of the process nodes of the integrated circuit. Moreover, in the fields of precision optical element processing, micro-electro-mechanical systems (MEMS), biomedical devices, high-end material surface analysis and the like, the high-precision morphology detection is also in urgent need. The traditional morphology detection device mainly comprises high-precision microscopes such as a Scanning Electron Microscope (SEM), an Atomic Force Microscope (AFM), a confocal microscope and the like, and the precision of the microscopes can reach the nanometer level, but the problems of high cost, large equipment volume, low detection speed, point measurement limitation, inconvenience in on-site online measurement and the like exist in the conventional morphology detection device. To overcome the limitations described above, interferometry has been developed. The basic principle of interferometry is that physical quantity information such as morphology, displacement and the like is modulated into parameters such as light intensity, phase and the like of an optical signal through the interference effect of an optical wave. When two or more coherent light waves are superimposed, the distribution of interference fringes is closely related to the optical path difference, and the optical path difference directly reflects the shape or displacement change of the measured object. The phase information in the interference optical signal can be accurately extracted through the high-precision optical detector and the signal processing algorithm, so that the shape or displacement change of the measured object can be solved, and the high-precision measurement of nano-scale or even sub-nano-scale is realized. The interferometry has the advantages of relatively simple system structure, lower cost and nano-scale precision. Common methods include white light interferometry, which uses a broadband light source, and swept-frequency interferometry, which uses swept-frequency lasers, both of which enable high-precision topography reconstruction. However, the method is still limited to single-point measurement at present, and the surface shape measurement needs to be realized by a scanning mechanism, so that the detection efficiency is affected to a certain extent. Disclosure of Invention The invention aims to provide a morphology displacement measurement system based on sweep frequency laser interference, which comprises a sweep frequency light source, a coupler, a reference arm, a measurement arm, a collimator, a blazed grating I, a blazed grating II, a photoelectric detector and a data acquisition module. The continuous laser emitted by the sweep frequency light source enters the coupler and is divided into two paths in the coupler, wherein one path is used as reference light and enters the reference arm. One path is used as measuring light and enters the measuring arm. The measuring arm is connected with the collimator. The measuring light enters a collimator through a measuring arm, the collimator is utilized for collimation, and then the collimated measuring light is vertically emitted to the blazed grating I. The blazed grating I disperses the continuous measurement light which is perpendicularly incident, so that the continuous measurement light is separated into a plurality of dispersed lights with different frequencies, and then the dispersed lights with different frequencies are irradiated to different positions on the blazed grating II. The blazed grating II is used for correcting the angle of the scattered light and vertically shooting the scattered light with a plurality of different frequencies to the surface of the target to be detected. The object to be measured is arranged right below the blazed grating II. The dispersion light is reflected after being irradiated to the target to be detected, and returns to the coupler along the original light path to interfere with the re