An extinction-type ellipsometer
By employing multiple symmetrically arranged polarization arms and polarization detection arms in the extinction ellipsometer, and combining them with an autocollimator for angle tracing, the problem of insufficient measurement accuracy and stability of traditional extinction ellipsometers is solved, and rapid and high-precision measurement is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NATIONAL INSTITUTE OF METROLOGY CHINA
- Filing Date
- 2024-09-29
- Publication Date
- 2026-06-23
AI Technical Summary
Traditional extinction ellipsometers have shortcomings in measurement accuracy and stability, and their measurement speed is relatively slow.
By employing multiple symmetrically arranged polarization arms and polarization detection arms, combined with an autocollimator and a high-precision calibration system, the origin of the polarization angle, polarization detection angle, and incident angle can be traced, thereby improving measurement accuracy and stability.
It enables rapid measurement of elliptic parameters, improves measurement accuracy and stability, and shortens measurement time.
Smart Images
Figure CN120064142B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of elliptic measurement technology, and in particular to an extinction-type ellipticometer. Background Technology
[0002] Ellipsometry, as an important tool for measuring the optical properties of materials, has a profound impact on scientific research and industrial applications due to its accuracy and reliability. However, traditional ellipsometers still have limitations in some aspects, especially in measurement accuracy and stability.
[0003] To overcome these challenges, extinction ellipsometers were developed. Extinction ellipsometers employ unique extinction technology, achieving high-precision measurement of material optical properties by precisely controlling the polarization state and propagation path of light; however, extinction ellipsometers require adjusting multiple angles to find the extinction point, resulting in longer measurement times and slower measurement speeds.
[0004] Therefore, there is an urgent need to design an extinction ellipsometer that can improve measurement speed. Summary of the Invention
[0005] The purpose of this invention is to provide an extinction-type ellipsometer to solve the problems existing in the prior art. By employing multiple symmetrically arranged polarization arms and polarization detection arms, it is possible to trace the source of three important angles: polarization angle, polarization detection angle, and incident angle, thereby improving measurement accuracy and stability.
[0006] To achieve the above objectives, the present invention provides the following solution:
[0007] This invention provides an extinction-type ellipsometer, comprising:
[0008] The base is made of marble, which provides better stability.
[0009] A wafer stage, which is mounted on a base, is used to adsorb and fix the sample to be tested, and can move the sample to be tested in multiple dimensions.
[0010] The mounting bracket is fixedly mounted on the base. It has multiple inclined polarization arms evenly arranged on one side and multiple polarization detection arms corresponding to the polarization arms on the other side. The polarization arms and the corresponding polarization detection arms are used to measure the ellipsoid parameters of the sample under test at different incident angles.
[0011] An autocollimator, mounted on the mounting bracket and positioned directly above the wafer stage, is used to correct the levelness of the sample surface. The autocollimator's lens faces downwards, and during the calibration of the sample's level, the autocollimator is aligned with the sample's surface. The display interface of the autocollimator allows the user to determine whether the sample is level relative to the autocollimator.
[0012] In one embodiment, the polarizing arm includes a coaxially arranged laser source, a brushless polarizing motor, a polarizer, and a phase retarder. The laser source is used to generate linearly polarized light. The polarizer is mounted on the shaft of the brushless polarizing motor. During the rotation of the brushless polarizing motor, the surface of the polarizer is always perpendicular to the propagation direction of the linearly polarized light. After passing through the polarizer, the linearly polarized light generates first linearly polarized light with a defined polarization angle. The phase retarder can convert the first linearly polarized light into circularly polarized light and incident it onto the sample to be tested.
[0013] In one embodiment, the polarization analyzer arm includes a brushless polarization motor, a polarizer, an unpolarized beam splitter, a polarization meter, and a photodetector. The polarizer is mounted on the shaft of the brushless polarization motor, and the brushless polarization motor, polarizer, and photodetector are coaxially arranged within the polarization analyzer arm. Light emitted from the polarization arm is reflected by the surface of the sample under test and received by the polarization analyzer arm, becoming second linearly polarized light that enters the unpolarized beam splitter. The unpolarized beam splitter splits the second linearly polarized light into two beams: one beam enters the polarization meter, and the other beam, after passing through the brushless polarization motor and the polarizer, enters the photodetector. The photodetector detects the intensity of the second linearly polarized light after passing through the polarizer, converts it into an electrical signal, and can find the minimum intensity angle. The polarizer can be used to find the angle perpendicular to the second linearly polarized light; when the direction of the polarizer is perpendicular to the polarization direction of the second linearly polarized light, the intensity of the second linearly polarized light after passing through the polarizer is zero. The polarization meter can determine the polarization state of the reflected light.
[0014] In one embodiment, the laser source includes a helium-neon laser, and each of the polarizing arms is provided with one of the helium-neon lasers.
[0015] In one embodiment, the mounting bracket has three polarization arms on one side, and the laser source includes a helium-neon laser. The helium-neon laser is connected to a first optical fiber and a second optical fiber through a laser beam splitter. The second optical fiber is connected to a third optical fiber and a fourth optical fiber through a laser beam splitter. The first optical fiber, the third optical fiber, and the fourth optical fiber are respectively connected to the three polarization arms.
[0016] In one embodiment, the mounting bracket has three polarizing arms on one side. The laser source includes a helium-neon laser. The laser emitted from the helium-neon laser is split into a first laser beam and a second laser beam by a beam splitter. The second laser beam is split into a third laser beam and a fourth laser beam by another beam splitter. The first laser beam enters the first polarizing arm. The third laser beam is reflected by a mirror and enters the second polarizing arm. The fourth laser beam is reflected by two mirrors and enters the third polarizing arm.
[0017] In one embodiment, the three biasing arms include biasing arm one, biasing arm two, and biasing arm three, and biasing arm one, biasing arm two, and biasing arm three have the same initial state; the three polarization detection arms include polarization detection arm one, polarization detection arm two, and polarization detection arm three, and polarization detection arm one, polarization arm two, and polarization detection arm three have the same initial state. Biasing arm one and polarization detection arm one are symmetrical with respect to the instrument's central axis. Biasing arm two and polarization detection arm two are symmetrical with respect to the instrument's central axis. Biasing arm three and polarization detection arm three are symmetrical with respect to the instrument's central axis.
[0018] Among them, polarization arm one and polarization arm one are used to measure the ellipsoidal parameters when the incident angle is 45 degrees. These ellipsoidal parameters are mainly used to calculate the number of thickness cycles. Polarization arm two and polarization arm two are used to measure the ellipsoidal parameters when the incident angle is 70 degrees. These ellipsoidal parameters are mainly used to calculate the film thickness outside the cycle. Polarization arm three and polarization arm three are used to measure the ellipsoidal parameters in the initial state.
[0019] In one embodiment, the mounting frame includes two arches symmetrically arranged on the base, which are fixedly connected by a connecting block, the bottom of which is fixedly connected to the base; the autocollimator is fixedly mounted on the top of the two arches; a measuring arm mounting base is provided on the side wall of the arch, and the offset arm and the offset detection arm are both mounted on the measuring arm mounting base. The device is placed between the two arches by the cooperation of the front and rear arches to ensure the stability of the device during operation.
[0020] In one embodiment, the phase retarder is arranged concentrically with the polarizer; the surface of the phase retarder is always perpendicular to the propagation direction of the linearly polarized light, and the fast axis inside the phase retarder is at a 45-degree angle to the polarization direction of the first linearly polarized light.
[0021] In one embodiment, the arch includes a semi-circular arch portion, the bottom of which is connected to a column with a rectangular cross-section, the bottom of which is connected to the base; the two arch portions are arranged concentrically, and the distance between the two arches is 400mm.
[0022] In one embodiment, the wafer stage is capable of horizontal movement of the sample under test within a range of 300mm×300mm, vertical lifting and lowering of 10mm, and omnidirectional pitch of ±2°.
[0023] The present invention achieves the following technical effects compared to the prior art:
[0024] This invention employs a combination of three elliptic lifting arms and three elliptic checking arms to achieve rapid measurement of the ellipticity parameters, the lifting angle and the checking angle. A high-precision autocollimator is used to calibrate the horizontal state and incident angle of the sample under test, further improving the accuracy of the incident angle. The mounting frame adopts a double-arch structure, which enables stable installation of the lifting and checking arms, unaffected by their gravity. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 This is a schematic diagram of the extinction type ellipsometer of the present invention;
[0027] Figure 2 This is a schematic diagram of the arch structure and base in this invention;
[0028] Figure 3 This is a schematic diagram of the first type of laser source in this invention;
[0029] Figure 4 This is a schematic diagram of the second type of laser source in this invention;
[0030] Figure 5 This is a schematic diagram of the third type of laser source in this invention.
[0031] Explanation of reference numerals in the attached diagram: 1-Polarizing arm one, 2-Polarizing arm two, 3-Polarizing arm three, 4-Arch, 5-Base, 6-Autocollimator, 7-Polarizing arm one, 8-Polarizing arm two, 9-Polarizing arm three, 10-Wafer stage, 11-Connecting block, 12-Measuring arm mounting base, 13-Helium-neon laser, 14-Laser beam splitter, 15-Fiber optic cable, 16-Reflector, 17-Beam splitter. Detailed Implementation
[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0033] The purpose of this invention is to provide an extinction-type ellipsometer to solve the problems existing in the prior art. By employing multiple symmetrically arranged polarization arms and polarization detection arms, it is possible to trace the source of three important angles: polarization angle, polarization detection angle, and incident angle, thereby improving measurement accuracy and stability.
[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0035] refer to Figure 1 and Figure 2As shown, this invention provides an extinction-type ellipsometer, including a base 5 made of marble, which mainly serves as the overall base, providing stability and vibration isolation. Two arches are symmetrically arranged on the base. A first elliptic arm 1, a second elliptic arm 2, and a third elliptic arm 3, acting as signal transmitting devices, are mounted on the left-side measuring arm mounting base 12 between the two arches 4. A first elliptic arm 7, a second elliptic arm 8, and a third elliptic arm 9, acting as signal receiving devices, are mounted on the right-side measuring arm mounting base 12 between the two arches 4. The archway 4 is connected to the connecting block 11 via four long screws. The connecting block 11 is connected to the base 5 via four countersunk screw holes. The front and rear sides of the bias arm and the detection arm each have four through holes, which are connected to the four-axis base via screws. The autocollimator 6 is mounted on top of the archway 4, directly above the wafer stage 10, and is used to correct the levelness of the sample surface. The lens of the autocollimator 6 points downwards. During the calibration of the sample's level, the autocollimator 6 is aligned with the sample surface. The display interface of the autocollimator 6 allows the system to determine whether the sample is level relative to the autocollimator 6. When the photoelectric sensor in the autocollimator display interface is centered, the sample surface is considered level. The wafer stage 10 is mounted on the base 5 and is used to adsorb and fix the sample, and can move the sample in multiple dimensions. The wafer stage 10 uses a ceramic vacuum chuck for adsorption, with a quincunx layout of the adsorption ports, enabling non-destructive testing while reducing warpage of the sample surface during adsorption. The wafer stage 10 uses three vertically arranged pen-shaped motors for lifting and tilting adjustment. When the three pen-shaped motors move the same distance, the vertical lifting movement of the sample is achieved, with a lifting range of 10mm. When the three pen-shaped motors move different distances, the tilting adjustment of the sample is achieved. This tilting adjustment can achieve omnidirectional adjustment, with an adjustment range of 2°. The bottom of the wafer stage 10 is an XY-axis horizontal moving platform. The top of the pen-shaped motor is connected to the bottom of the wafer stage 10. The pen-shaped motor is a miniature electric cylinder with a pen-shaped structure. The three miniature electric cylinders are evenly distributed at different positions on the bottom of the wafer stage 10 and are symmetrically distributed. When the cylinder shafts of the three miniature electric cylinders extend and retract by the same length, they can drive the wafer stage 10 to extend and retract synchronously, thereby realizing the vertical lifting and lowering movement of the sample under test. When the cylinder shafts of the three miniature electric cylinders extend and retract by different lengths, they can drive the corresponding positions of the wafer stage 10 to rise and fall by different heights, which is externally manifested as the pitch movement of the wafer stage 10, thereby realizing the pitch adjustment of the sample under test. This pitch adjustment can achieve omnidirectional adjustment.The pen-shaped motor is mounted on the bottom of the XY-axis horizontal moving platform. The XY-axis horizontal moving platform can drive the pen-shaped motor and the wafer stage 10 to move horizontally synchronously. The moving range is 300mm*300mm, which can meet the omnidirectional measurement of 4-inch, 6-inch, 8-inch and 12-inch samples. The XY-axis horizontal moving platform has a known structure and can be driven by a ball screw and nut structure or by a horizontally arranged micro electric cylinder. Both can realize the movement of the pen-shaped motor and the wafer stage 10 in the horizontal X and Y directions.
[0036] In a preferred embodiment, an autocollimator 6 and a high-precision reflecting prism are used together. The high-precision reflecting prism is placed on the wafer stage 10. The laser emitted from the laser is reflected by the reflecting prism and then enters the autocollimator 6. When the photoelectric image on the display interface of the autocollimator 6 is located at the center of the image, it is determined that the incident angle value is the reflection angle of the reflecting prism.
[0037] In this embodiment, all polarizing arms are shielded from external light to reduce the influence of ambient light on the laser state. Polarizing arms 1, 2, and 3 have identical structures, each including a laser source, a brushless polarizing motor, a polarizing plate, and a phase retarder. In one embodiment, the phase retarder and the polarizing plate are arranged concentrically. The surface of the phase retarder is always perpendicular to the propagation direction of the linearly polarized light, and the fast axis inside the phase retarder is at a 45-degree angle to the polarization direction of the first linearly polarized light. The phase retarder uses an automatic waveplate, i.e., a liquid crystal variable retarder, filled with a liquid crystal molecular solution. Without voltage, the internal molecules are orderly arranged, and no change in polarization state occurs after the laser passes through. With voltage applied, the internal molecules are arranged according to the electric field. The delay effect of the waveplate on the laser varies under different voltages. The polarizing plate uses a nanoparticle thin-film linear polarizer, which has a high extinction ratio and a high laser damage threshold. Under a 633nm wavelength laser, it has a 10 6 The extinction ratio is determined by ensuring that the rotation angle of the brushless polarizing motor is equal to the polarization angle of the polarizer. The polarizer is fixed in a threaded housing, and the threaded housing is connected to the brushless polarizing motor via a threaded connection. The base of the brushless polarizing motor adopts an XY-axis pitch base. By using the pitch base, the surface of the polarizer on the brushless polarizing motor is adjusted to be perpendicular to the emitted laser light from the helium-neon laser 13. Before measurement, the brushless polarizing motor is rotated to the following state: the linearly polarized light emitted from the laser, after passing through the polarizer, changes from linearly polarized light with a certain polarization angle to linearly polarized light with a polarization angle of 0°.
[0038] The initial angles of the brushless polarizing motors in all polarizing arms are the same. The wavelengths of the lasers emitted by the helium-neon lasers 13 in all polarizing arms are the same. The fast shafts of the phase retarders in polarizing arms 1 and 2 rotate at the same angle. The laser source is used to generate linearly polarized light. A polarizer is provided on the brushless polarizing motor. During the rotation of the brushless polarizing motor, the surface of the polarizer is always perpendicular to the propagation direction of the linearly polarized light. After passing through the polarizer, the linearly polarized light generates first linearly polarized light with a defined polarization angle. The phase retarder can convert the first linearly polarized light into circularly polarized light and incident it on the sample to be tested.
[0039] In one embodiment, polarization arm 7, polarization arm 8, and polarization arm 9 have the same structure, each including a polarization brushless motor, a polarizer, an unpolarized beam splitter 17, a polarization meter, and a photodetector. The initial angle of the polarization brushless motor in all polarization arms is the same.
[0040] Preferably, the polarization testers within all polarization arms are in the same relative position. A photodetector is used to detect the intensity of the second linearly polarized light after passing through the analyzer, converting it into an electrical signal to find the minimum intensity angle. The light emitted from the polarization arm, after reflection from the surface of the sample under test, is received by the analyzer and enters the unpolarized beam splitter 17 as the second linearly polarized light. The unpolarized beam splitter 17 splits the second linearly polarized light into two beams: one enters the polarization tester, and the other enters the analyzer on the brushless polarization motor and is received by the photodetector. The analyzer can find the angle perpendicular to the second linearly polarized light. When the analyzer direction is perpendicular to the polarization direction of the second linearly polarized light, the intensity of the second linearly polarized light after passing through the analyzer is zero. The polarization tester can determine the polarization state of the reflected light. An XY-axis pitch structure is installed at the bottom of the polarization tester. Through the pitch structure, the plane receiving the signal inside the polarization tester is adjusted to be perpendicular to the propagation direction of the laser. In the initial angle measurement stage, this is used to determine the initial polarization angle of 0° and to determine whether the linearly polarized light becomes circularly polarized after passing through the phase delayer.
[0041] like Figure 3 As shown, in one embodiment, the laser source includes a helium-neon laser 13, with a helium-neon laser 13 disposed on each polarizing arm. The polarizing arm employs a stable helium-neon laser 13, which, in intensity-stable mode, can emit linearly polarized light with a wavelength of 632.992 nm and constant output power, with a beam diameter of 0.65 ± 0.05 mm. The base of the helium-neon laser 13 is a pitch mechanism, which can achieve one-dimensional pitch adjustment with an adjustment range of ± 2°, used to adjust the emission direction of the laser, ensuring that the linearly polarized light emitted by the stable helium-neon laser 13 can be incident on the sample surface at a set incident angle.
[0042] like Figure 4As shown, in one embodiment, the laser source includes a helium-neon laser 13. The helium-neon laser 13 is connected to a first optical fiber 15 and a second optical fiber 15 via a laser beam splitter 14. The second optical fiber 15 is connected to a third optical fiber 15 and a fourth optical fiber 15 via a laser beam splitter 14. The first optical fiber 15, the third optical fiber 15 and the fourth optical fiber 15 are respectively connected to three polarizing arms.
[0043] like Figure 5 As shown, in one embodiment, the laser source includes a helium-neon laser 13. The laser emitted from the helium-neon laser 13 is split into a first laser beam and a second laser beam by a beam splitter 17. The second laser beam is split into a third laser beam and a fourth laser beam by another beam splitter 17. The first laser beam and the third laser beam enter two polarizing arms respectively. The fourth laser beam enters a third polarizing arm after being reflected by a reflector 16.
[0044] In a preferred embodiment, polarization arm 1 and polarization detector arm 7 are used to measure the ellipticity parameters when the incident angle is 45 degrees. These ellipticity parameters are mainly used to calculate the number of thickness cycles. Polarization arm 2 and polarization detector arm 8 are used to measure the ellipticity parameters when the incident angle is 70 degrees. These ellipticity parameters are mainly used to calculate the film thickness outside the cycle. Polarization arm 3 and polarization detector arm 9 are used to measure the ellipticity parameters in the initial state.
[0045] In one embodiment, the arch 4 includes an arch section, which is a semi-circular ring. The bottom of the arch section is connected to a column with a rectangular cross-section, and the bottom of the column is connected to the base. The two arch sections are arranged concentrically, and the distance between the two arches 4 is 400mm.
[0046] In practical applications, the primary function of the high-precision autocollimator 6 system is to adjust the horizontal state of the sample surface, and the secondary function is to calibrate the true state of the incident angle and reflection angle. To adjust the sample surface level, the sample is first mounted on a ceramic vacuum chuck. The signal light emitted from the autocollimator 6 is perpendicular to the sample surface. After reflection from the sample surface, the signal light is received internally by the autocollimator 6. On the display interface of the autocollimator 6, when the light spot is centered, it indicates that the sample has been adjusted to a horizontal state relative to the autocollimator 6. When the light spot is not centered, the three pen motors inside the stage need to be adjusted individually until the light spot is centered. When calibrating the incident angle and reflection angle, first adjust the stage to the height of the center of the arch 4. Using the autocollimator 6 and the high-precision prism, the light emitted from the autocollimator 6 is reflected at a specific angle after passing through the high-precision prism. After reflection, it passes through the polarizer arm or analyzer arm and is reflected back by the lens on the polarizer arm or analyzer arm. On the display interface of the autocollimator 6, when the light spot is located in the center of the display interface, it indicates that the incident angle and reflection angle have been calibrated. When the light spot is not located in the center of the display interface, it is necessary to adjust the angle of the internal optical path of the polarizer arm and analyzer arm until the light spot is in the center position.
[0047] In practical applications, the three polarizing arms need to be calibrated to the same state before installation. Specifically, the same polarization tester is used to test the light emitted from the polarizing arms. The polarizing arms are directly aligned with the same polarization tester. When the brushless polarizing motors of the three polarizing arms are adjusted to the same angle, the deviation between the polarization angles displayed in the polarization tester does not exceed 0.5%, which means that the initial state calibration of the three polarizing arms is complete.
[0048] In practical applications, the fast axis of the phase retarder inside polarizer arm 1 and polarizer arm 2 is at the same angle to the polarization direction of the propagating laser. Specifically, the same laser and polarizer are used to generate linearly polarized light with the same polarization angle. These two phase retarders will convert the linearly polarized light into elliptically polarized light. When the deviation between the elliptically polarized light measured by the two elliptically polarized lights does not exceed 0.5%, it indicates that the two phase retarders have been calibrated.
[0049] In practical applications, the three polarization analyzers also need to be calibrated to the same state before installation. Specifically, the same polarization analyzer is used to emit polarized light, and the same polarization analyzer is directly aligned with the three polarization analyzers. When the parameters displayed by the polarization tester and the angle displayed by the brushless polarization motor in all polarization analyzers do not deviate from each other by more than 0.5%, it is judged that the initial state calibration of the three polarization analyzers is completed.
[0050] In practical applications, the polarizer arm 3 (3) and the analyzer arm 9 (9) are aligned horizontally and symmetrical with respect to the instrument's central axis. This dual-arm structure is used to measure the initial polarization state. The internal optical path consists of linearly polarized light emitted from a helium-neon laser 13, which is converted into linearly polarized light with a specific polarization angle after passing through the polarizer. During this process, the polarization tester in the analyzer arm measures the polarization angle. When the linear polarization angle displayed on the polarization tester's interface is 0 degrees, it indicates the initial polarization state. The rotation angle displayed by the brushless polarizer motor in this state is the initial polarization angle.
[0051] In practical applications, polarizing arm 2 and polarizing arm 8, and polarizing arm 3 and polarizing arm 9 are symmetrical with respect to the instrument's central axis. The function of these two sets of dual-arm structures is to measure the polarization and polarization detection states when the incident angles are 45 degrees and 70 degrees. The internal optical path is that the linearly polarized light emitted by the helium-neon laser 13 becomes linearly polarized light with a certain polarization angle after passing through the polarizer, and then becomes circularly polarized light after passing through the phase delayer. After being reflected by the sample surface, the circularly polarized light becomes elliptically polarized light. At this time, the polarizer motor is adjusted, and after rotating a certain angle, the reflected elliptically polarized light is converted back into linearly polarized light. In this process, the angle of rotation of the brushless polarizing motor is the polarization angle, which is expressed in the algorithm as the angle of the brushless polarizing motor after adjustment minus the initial angle of the brushless polarizing motor. The polarization angle of the linearly polarized light detected by the polarization tester is the polarization detection angle.
[0052] The polarization angle and analyzer angle measured at an incident angle of 70 degrees are mainly used to calculate the film thickness outside the cycle. The polarization angle and analyzer angle measured at an incident angle of 45 degrees are mainly used to calculate the number of film thickness cycles. Specifically, by combining the parameter of the 70-degree incident angle, a univariate unknown equation is established, and solving the equation yields the number of thickness cycles. After obtaining the number of thickness cycles and the thickness outside the cycle, the formula D = n * T + d is used, where D is the total film thickness, n is the number of cycles, T is the cycle thickness, and d is the thickness outside the cycle.
[0053] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.
Claims
1. An extinction-type ellipsometer, characterized in that: include: Base; A wafer stage, which is mounted on a base, is used to adsorb and fix the sample to be tested, and can move the sample to be tested in multiple dimensions. The wafer stage uses a ceramic vacuum chuck for adsorption, and the adsorption port adopts a plum blossom-shaped layout, which can realize non-destructive testing and reduce the warping deformation of the sample surface during the adsorption process. A mounting frame, fixedly mounted on the base, has multiple inclined polarizing arms evenly arranged on one side and multiple polarizing analyzers corresponding to the polarizing arms on the other side. Each polarizing arm includes a coaxially arranged laser source, a brushless polarizing motor, a polarizing plate, and a phase delayer. Each polarizing analyzer includes a brushless polarizing motor, a polarizing plate, an unpolarized beam splitter, a polarization meter, and a photodetector. The polarizing arms and their corresponding analyzers are used to measure the ellipsoidal parameters of the sample under test at different incident angles. Three polarizing arms are located on one side of the mounting frame. The mounting frame includes two symmetrically arranged arches on the base, which are fixedly connected by a connecting block. The bottom of the connecting block is fixedly connected to the base. An autocollimator is fixedly mounted on the top of the two arches. A measuring arm mounting base is provided on the side wall of the arches, and both the polarizing arms and the analyzers are mounted on the measuring arm mounting base. An autocollimator, mounted on the mounting bracket and positioned directly above the wafer stage, is used to calibrate the levelness of the sample surface under test. The wafer stage enables the sample to move horizontally within a 300mm×300mm range, move vertically by 10mm, and tilt in all directions by ±2°. The archway includes a semi-circular archway, and a rectangular column is connected to the bottom of the archway. The bottom of the column is connected to the base. The two archways are arranged concentrically, and the distance between the two archways is 400mm. It also includes a prism, through which the light emitted from the autocollimator can be reflected at a specific angle to the polarizing arm or the analyzer arm, and then reflected back to the autocollimator by the lenses on the polarizing arm or the analyzer arm. When the light spot reflected back to the autocollimator is located at the center of the autocollimator's display interface, it indicates that the incident angle and reflection angle have been calibrated. When the light spot is not located at the center of the autocollimator's display interface, it is necessary to adjust the angle of the internal optical path of the polarizing arm and the analyzer arm.
2. The extinction-type ellipsometer according to claim 1, characterized in that: The laser source is used to generate linearly polarized light. A polarizer is provided on the shaft of the brushless motor. During the rotation of the brushless motor, the surface of the polarizer is always perpendicular to the propagation direction of the linearly polarized light. After passing through the polarizer, the linearly polarized light generates first linearly polarized light with a defined polarization angle. The phase delayer can convert the first linearly polarized light into circularly polarized light and incident it on the sample to be tested.
3. The extinction-type ellipsometer according to claim 1, characterized in that: The polarizer is mounted on the shaft of the brushless polarizing motor, and the brushless polarizing motor, the polarizer, and the photodetector are arranged coaxially. The light emitted from the polarizing arm is reflected by the surface of the sample under test and received by the polarizing arm, and enters the unpolarized beam splitter as a second linearly polarized light. The unpolarized beam splitter splits the second linearly polarized light into two beams: one beam enters the polarization tester, and the other beam enters the photodetector after passing through the brushless polarizing motor and the polarizer.
4. The extinction-type ellipsometer according to claim 2, characterized in that: The laser source includes a helium-neon laser, and each of the polarizing arms is equipped with one of the helium-neon lasers.
5. The extinction-type ellipsometer according to claim 2, characterized in that: The laser source includes a helium-neon laser, which is connected to a first optical fiber and a second optical fiber via a laser beam splitter. The second optical fiber is connected to a third optical fiber and a fourth optical fiber via a laser beam splitter. The first, third, and fourth optical fibers are respectively connected to the three polarizing arms.
6. The extinction-type ellipsometer according to claim 2, characterized in that: The laser source includes a helium-neon laser. The laser emitted from the helium-neon laser is split into a first laser beam and a second laser beam by a beam splitter. The second laser beam is split into a third laser beam and a fourth laser beam by another beam splitter. The first laser beam enters the first polarizing arm. The third laser beam is reflected by a mirror and enters the second polarizing arm. The fourth laser beam is reflected by two mirrors and enters the third polarizing arm.
7. The extinction-type ellipsometer according to claim 2, characterized in that: The phase retarder is arranged concentrically with the polarizer; the surface of the phase retarder is always perpendicular to the propagation direction of the linearly polarized light, and the fast axis inside the phase retarder is at a 45-degree angle to the polarization direction of the first linearly polarized light.