Extinction ellipsometer

Abstract

The invention discloses an extinction ellipsometer, which relates to the technical field of ellipsometry, and comprises a base, a wafer objective table and a mounting rack, the wafer objective table is arranged on the base, is used for adsorbing and fixing a to-be-tested sample and can drive the to-be-tested sample to perform multi-dimensional movement; the mounting frame is fixedly arranged on the base, one side of the mounting frame is uniformly provided with a plurality of obliquely arranged polarizing arms, and the other side of the mounting frame is provided with a plurality of polarization detecting arms in one-to-one correspondence with the polarizing arms; the polarizing arm and the corresponding polarization detection arm are used for measuring ellipsometry parameters of the sample to be measured at different incident angles; and the autocollimator is arranged on the mounting frame, is positioned right above the wafer objective table, and is used for correcting the levelness of the surface of the sample to be detected. According to the extinction ellipsometer provided by the invention, the polarization arms and the polarization detection arms which are symmetrically arranged are adopted, so that three important angles, namely a polarization angle, a polarization detection angle and an incident angle, can be traced, and the measurement precision and the stability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ellipsometry, and particularly to a null ellipsometer. Background Art

[0002] As an important tool for measuring the optical properties of materials, the accuracy and reliability of an ellipsometer have a profound impact on scientific research and industrial applications. However, traditional ellipsometers still have limitations in some aspects, especially in measurement accuracy and stability.

[0003] To overcome these challenges, the null ellipsometer came into being. The null ellipsometer adopts a unique extinction technology, and through precise control of the polarization state and propagation path of light, high-precision measurement of the optical properties of materials is achieved; however, the null ellipsometer needs to adjust multiple angles to find the extinction point, resulting in a long measurement time and a slow measurement speed.

[0004] Based on this, there is an urgent need to design a null ellipsometer that can improve the measurement speed. Summary of the Invention

[0005] The purpose of the present invention is to provide a null ellipsometer to solve the problems existing in the above-mentioned prior art. By adopting multiple symmetrically arranged polarizer arms and analyzer arms, the traceability of three important angles, namely the polarization angle, the analyzer angle, and the incident angle, can be realized, improving the measurement accuracy and stability.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] The present invention provides a null ellipsometer, comprising:

[0008] A base, which is made of marble material and has better stability;

[0009] A wafer stage, which is arranged on the base, used for adsorbing and fixing the sample to be measured, and capable of driving the sample to be measured to move in multiple dimensions;

[0010] A mounting rack, fixedly arranged on the base, with a plurality of inclined polarizer arms uniformly arranged on one side and a plurality of analyzer arms corresponding to the polarizer arms one by one on the other side; the polarizer arms and the corresponding analyzer arms are used for measuring the ellipsometry parameters of the sample to be measured at different incident angles;

[0011] An autocollimator, arranged on the mounting rack and located directly above the wafer stage, used for correcting the flatness of the surface of the sample to be measured; the lens of the autocollimator faces downward. During the process of calibrating the horizontal plane of the sample to be measured, the autocollimator is aligned with the surface of the sample to be measured. Through the display interface of the autocollimator, it can be judged whether the sample to be measured is in a state horizontal relative to the autocollimator.

[0012] In one embodiment, the polarizing arm includes a laser source, a polarization brushless motor, a polarizer, and a phase retarder arranged coaxially. The laser source is used to generate linearly polarized light. A polarizer is provided on the rotating shaft of the polarization brushless motor. During the rotation of the polarization 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 a first linearly polarized light with a determined polarization angle. The phase retarder can convert the first linearly polarized light into circularly polarized light and incident on the sample to be measured.

[0013] In one embodiment, the analyzing arm includes an analyzing brushless motor, an analyzer, an unpolarized beam splitter, a polarization tester, and a photodetector. The analyzer is provided on the rotating shaft of the analyzing brushless motor. The analyzing brushless motor, the analyzer, and the photodetector are arranged coaxially in the analyzing arm. The light emitted from the polarizing arm is reflected by the surface of the sample to be measured and can be received by the analyzing arm and enter the unpolarized beam splitter as a second linearly polarized light. The unpolarized beam splitter divides the second linearly polarized light into two beams. One beam is incident on the polarization tester, and the other beam enters the photodetector after passing through the analyzing brushless motor and the analyzer. The photodetector is used to detect the light intensity of the second linearly polarized light after passing through the analyzer, convert it into an electrical signal, and can find the minimum light intensity angle. The angle perpendicular to the second linearly polarized light can be found through the analyzer. When the direction of the analyzer is perpendicular to the polarization direction of the second linearly polarized light, the light intensity of the second linearly polarized light after passing through the analyzer is zero. The polarization state of the reflected light can be judged through the polarization tester.

[0014] In one embodiment, the laser source includes a helium-neon laser, and one helium-neon laser is respectively provided on each polarizing arm.

[0015] In one embodiment, three polarizing arms are provided on one side of the mounting frame. The laser source includes a helium-neon laser. The helium-neon laser is connected with a first optical fiber and a second optical fiber through a laser beam splitter. The second optical fiber is connected with 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 polarizing arms correspondingly.

[0016] In one embodiment, three polarizing arms are provided on one side of the mounting frame. The laser source includes a helium-neon laser. The laser emitted by the helium-neon laser is divided into a first laser beam and a second laser beam through a beam splitter. The second laser beam is divided into a third laser beam and a fourth laser beam through another beam splitter. The first laser beam enters the first polarizing arm. The third laser beam enters the second polarizing arm after being reflected by a mirror. The fourth laser beam enters the third polarizing arm after being reflected by two mirrors.

[0017] In one embodiment, the three polarizing arms include the first polarizing arm, the second polarizing arm, and the third polarizing arm, and the initial states of the first polarizing arm, the second polarizing arm, and the third polarizing arm are the same; the three analyzing arms include the first analyzing arm, the second analyzing arm, and the third analyzing arm, and the initial states of the first analyzing arm, the second analyzing arm, and the third analyzing arm are the same. The first polarizing arm and the first analyzing arm are axisymmetric with respect to the center axis of the instrument. The second polarizing arm and the second analyzing arm are axisymmetric with respect to the center axis of the instrument. The third polarizing arm and the third analyzing arm are axisymmetric with respect to the center axis of the instrument.

[0018] Among them, the first polarizing arm and the first analyzing arm are used to measure the ellipsometry parameters when the incident angle is 45 degrees, and this set of ellipsometry parameters is mainly used to calculate the thickness period number. The second polarizing arm and the second analyzing arm are used to measure the ellipsometry parameters when the incident angle is 70 degrees, and this set of ellipsometry parameters is mainly used to calculate the thickness of the film outside the period. The third polarizing arm and the third analyzing arm are used to measure the ellipsometry parameters in the initial state.

[0019] In one embodiment, the mounting frame includes two arches symmetrically arranged on the base, and the two arches are fixedly connected by a connecting block. The bottom of the connecting block is fixedly connected to the base; the autocollimator is fixedly arranged on the tops of the two arches; a measuring arm mounting base is provided on the side wall of the arch, and the polarizing arm and the analyzing arm are both mounted on the measuring arm mounting seat. By using the cooperation of the front and rear two arches, the device is placed between the two arches to ensure the stability of the device during operation.

[0020] In one embodiment, the phase retarder is concentrically arranged 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 forms a 45-degree angle with the polarization direction of the first linearly polarized light.

[0021] In one embodiment, the arch includes an arching part, the arching part is semi-circular ring-shaped, the bottom of the arching part is connected with a column with a rectangular cross-section structure, and the bottom of the column is connected to the base; the two arching parts are arranged concentrically, and the distance between the two arches is 400 mm.

[0022] In one embodiment, the wafer stage can realize the horizontal movement of the sample to be measured within the range of 300 mm × 300 mm, the vertical lifting of 10 mm, and the omnidirectional pitching of ±2°.

[0023] The present invention has achieved the following technical effects compared with the prior art:

[0024] The present invention adopts the combination of three polarizing arms and three analyzing arms, which can realize the rapid measurement of the polarization angle and the analyzing angle of the ellipsometry parameters. The high-precision autocollimator is used to calibrate the horizontal state and the incident angle of the sample to be measured, further improving the accuracy of the incident angle. The mounting frame adopts a double-arch structure, which can realize the stable installation of the polarizing arm and the analyzing arm without being affected by their gravity. Brief Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 Schematic diagram of the extinction ellipsometer of the present invention;

[0027] Figure 2 Schematic diagram of the arch structure and the base in the present invention;

[0028] Figure 3 Schematic diagram of the first laser source in the present invention;

[0029] Figure 4 Schematic diagram of the second laser source in the present invention;

[0030] Figure 5 Schematic diagram of the third laser source in the present invention.

[0031] Description of reference numerals: 1 - first polarizing arm, 2 - second polarizing arm, 3 - third polarizing arm, 4 - arch, 5 - base, 6 - autocollimator, 7 - first analyzing arm, 8 - second analyzing arm, 9 - third analyzing arm, 10 - wafer stage, 11 - connecting block, 12 - mounting base of the measuring arm, 13 - helium-neon laser, 14 - laser beam splitter, 15 - optical fiber, 16 - mirror, 17 - beam splitter. Detailed Description of the Invention

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0033] The purpose of the present invention is to provide an extinction ellipsometer to solve the problems existing in the above-mentioned prior art. By using multiple symmetrically arranged polarizing arms and analyzing arms, the traceability of three important angles, namely the polarization angle, the analyzing angle, and the incident angle, can be achieved, improving the measurement accuracy and stability.

[0034] In order to make the above-mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0035] Refer to Figure 1 andFigure 2As shown in the figure, the present invention provides a null ellipsometer, which includes a base 5 made of marble material, mainly serving as the overall base, capable of playing a role in stabilizing and isolating vibration; two arches are symmetrically arranged on the base. The polarizer arm 1, the polarizer arm 2, and the polarizer arm 3 serve as signal emitting devices and are installed on the measuring arm mounting base 12 on the left side between the two arches 4. The analyzer arm 1, the analyzer arm 2, and the analyzer arm 3 serve as signal receiving devices and are installed on the measuring arm mounting base 12 on the right side between the two arches 4. The arch 4 is connected to the connecting block 11 through four long screws, and the connecting block 11 is connected to the base 5 through four counterbored holes. Four through holes are provided on the front and rear sides of the polarizer arm and the analyzer arm, and are connected to the four-axis base through screws. The autocollimator 6 is installed on the top of the arch 4 and is located directly above the wafer stage 10, and is used to correct the levelness of the surface of the sample to be measured; the lens of the autocollimator 6 faces downward. During the process of calibrating the horizontal plane of the sample to be measured, the autocollimator 6 is aligned with the surface of the sample to be measured. Through the display interface of the autocollimator 6, it can be judged whether the sample to be measured is in a state horizontal relative to the autocollimator 6. When the photoelectric element in the display interface of the autocollimator is located at the center of the image, it is judged that the surface of the sample is in a horizontal state. The wafer stage 10 is arranged on the base 5, used to adsorb and fix the sample to be measured, and can drive the sample to be measured to move in multiple dimensions; the inside of the wafer stage 10 uses a ceramic vacuum chuck for adsorption, and the adsorption ports are arranged in a plum blossom pattern, which can realize non-destructive detection and at the same time reduce the warping deformation of the surface of the sample to be measured during the adsorption process. Three pen-shaped motors arranged vertically are used inside the wafer stage 10 for lifting and pitching adjustment. When the three pen-shaped motors move the same distance, the vertical lifting movement of the sample is realized, and the lifting range is 10 mm. When the moving distances of the three pen-shaped motors are different, the pitching adjustment of the sample is realized, and this pitching adjustment can realize omnidirectional adjustment, and the adjustment range is 2°. The bottom of the wafer stage 10 is an XY-axis horizontal movement platform. The top of the pen-shaped motor is connected to the bottom of the wafer stage 10. The pen-shaped motor is a micro electric cylinder with a pen-shaped structure. The three micro electric cylinders are evenly distributed at different positions at the bottom of the wafer stage 10 and are symmetrically distributed. Therefore, when the cylinder shafts of the three micro electric cylinders extend and contract by the same length, the wafer stage 10 can be driven to synchronously extend and contract, and then the vertical lifting movement of the sample to be measured is realized. When the cylinder shafts of the three micro electric cylinders extend and contract by different lengths, the wafer stage 10 can be driven to lift different heights at the corresponding positions, and the external manifestation is the pitching movement of the wafer stage 10, and then the pitching adjustment of the sample to be measured is realized, and this pitching adjustment can realize omnidirectional adjustment.The bottom of the pen-shaped motor is mounted on 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 full-range measurement of 4-inch, 6-inch, 8-inch, and 12-inch samples to be measured. The XY-axis horizontal moving platform is a known structure and can be driven by a lead screw nut structure or a horizontally arranged micro electric cylinder, both of which 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, a self-collimator 6 and a high-precision reflecting prism are used in cooperation. The high-precision reflecting prism is placed on the wafer stage 10. The laser emitted by the laser passes through the reflecting prism and then enters the self-collimator 6. When the photoelectric in the display interface of the self-collimator 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] All the polarizing arms in this embodiment are externally isolated from external light by a light-shielding cover to reduce the influence of ambient light on the laser state. The polarizing arm 1, the polarizing arm 2, and the polarizing arm 3 have the same structure and each includes a laser source, a polarization brushless motor, a polarizer, and a phase retarder. In one embodiment, the phase retarder is concentrically arranged 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 forms a 45-degree angle with the polarization direction of the first linearly polarized light. The phase retarder uses an automatic wave plate, that is, a liquid crystal variable retarder, which is filled with a liquid crystal molecular solution. In the case of no voltage applied, the internal molecules are arranged in an orderly manner, and the laser does not produce a change in the polarization state after passing through. In the case of voltage applied, the internal molecules are arranged according to the electric field. Under different voltages, the wave plate has different delaying effects on the laser. The polarizer uses a nanoparticle thin film linear polarizer, which has a high extinction ratio and a high laser damage threshold. At a laser wavelength of 633nm, it has 10 6 an extinction ratio. To ensure that the rotation angle of the polarization brushless motor is the polarization angle of the polarizer, the polarizer is fixed in the threaded housing, and the threaded housing and the polarization brushless motor are connected by threads. The base of the polarization brushless motor uses an XY-axis pitching base. Through the pitching base, the surface of the polarizer on the polarization brushless motor is adjusted to a state perpendicular to the emitted laser of the helium-neon laser 13. Before measurement, the polarization brushless motor is rotated to the following state: the linearly polarized light emitted by the laser becomes linearly polarized light with a polarization angle of 0° after passing through the polarizer.

[0038] The initial angles of the polarization brushless motors in all polarization arms are the same. The wavelengths of the laser light emitted by the helium-neon lasers 13 in all polarization arms are the same. The angles of rotation of the fast axes of the phase retarders in polarization arm one 1 and polarization arm two 2 are the same. The laser source is used to generate linearly polarized light. A polarizer is provided on the polarization brushless motor. During the rotation of the polarization brushless motor, the surface of the polarizer is always perpendicular to the propagation direction of the linearly polarized light; after the linearly polarized light passes through the polarizer, linearly polarized light with a determined polarization angle is generated. The phase retarder can change the linearly polarized light into circularly polarized light and incident on the sample to be measured.

[0039] In one embodiment, polarization analyzer arm one 7, polarization analyzer arm two 8, and polarization analyzer arm three 9 have the same structure, and each includes a polarization analysis brushless motor, a polarizer, an unbiased beam splitter 17, a polarization tester, and a photodetector. The initial angles of the polarization analysis brushless motors in all polarization analyzer arms are the same.

[0040] Preferably, the relative positions of the polarization testers in all polarization analyzer arms are the same. The photodetector is used to detect the light intensity of the second linearly polarized light after passing through the polarizer, convert it into an electrical signal, and can find the minimum light intensity angle; the light emitted from the polarization arm is reflected by the surface of the sample to be measured and can be received by the polarization analyzer arm and enter the unbiased beam splitter 17 as the second linearly polarized light. The unbiased beam splitter 17 divides the second linearly polarized light into two beams. One beam is incident on the polarization tester, and the other beam is received by the photodetector after passing through the polarizer on the polarization analysis brushless motor. The angle perpendicular to the second linearly polarized light can be found through the polarizer. When the direction of the polarizer is perpendicular to the polarization direction of the second linearly polarized light, the light intensity of the second linearly polarized light after passing through the polarizer is zero; the polarization state of the reflected light can be judged through the polarization tester. The bottom of the polarization tester is equipped with an XY-axis pitching structure. Through the pitching structure, the plane for receiving signals inside the polarization tester is adjusted to be perpendicular to the propagation direction of the laser. In the initial angle measurement stage, it is used for the judgment of the polarization angle of 0° and the judgment that the linearly polarized light becomes circularly polarized light after passing through the phase retarder.

[0041] As Figure 3 shown, in one embodiment, the laser source includes a helium-neon laser 13. A helium-neon laser 13 is respectively provided on each polarization arm. A stable-type helium-neon laser 13 is adopted inside the polarization arm. In the intensity stable mode, it can emit linearly polarized light with a constant output power and a wavelength of 632.992 nm, and the beam diameter is 0.65 ± 0.05 mm; the base of the helium-neon laser 13 is a pitching mechanism, and this pitching mechanism can achieve one-dimensional pitching adjustment with an adjustment range of ±2°, which is used to adjust the emission direction of the laser and can ensure that the linearly polarized light emitted by the stable-type helium-neon laser 13 can be incident on the sample surface at a set incident angle.

[0042] As 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 through a laser beam splitter 14. The second optical fiber 15 is connected to a third optical fiber 15 and a fourth optical fiber 15 through 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 polarization arms.

[0043] As Figure 5 As shown, in one embodiment, the laser source includes a helium-neon laser 13. The laser emitted by the helium-neon laser 13 is divided into a first laser beam and a second laser beam by a beam splitter 17. The second laser beam is divided into a third laser beam and a fourth laser beam by another beam splitter 17. The first laser beam and the third laser beam respectively enter two polarization arms, and the fourth laser beam enters the third polarization arm after being reflected by a mirror 16.

[0044] In the preferred solution of this embodiment, polarization arm one 1 and analyzer arm one 7 are used to measure the ellipsometry parameters when the incident angle is 45 degrees. This set of ellipsometry parameters is mainly used to calculate the thickness period number. Polarization arm two 2 and analyzer arm two 8 are used to measure the ellipsometry parameters when the incident angle is 70 degrees. This set of ellipsometry parameters is mainly used to calculate the thickness of the film outside the period. Polarization arm three 3 and analyzer arm three 9 are used to measure the ellipsometry parameters in the initial state.

[0045] In one embodiment, the arch 4 includes a springing part. The springing part is semi-circular ring-shaped. The bottom of the springing part is connected to a column with a rectangular cross-section structure. The bottom of the column is connected to the base; the two springing parts are arranged concentrically, and the distance between the two arches 4 is 400 mm.

[0046] In practical applications, the first function of the high-precision autocollimator 6 system is to adjust the horizontal state of the sample surface, and the second function is to calibrate the true states of the incident angle and the reflection angle. When adjusting the horizontal state of the sample surface, first mount the sample on the ceramic vacuum chuck. The signal light emitted by the autocollimator 6 is perpendicular to the sample surface. After being reflected by the sample surface, the signal light is received inside the autocollimator 6. On the display interface of the autocollimator 6, when the light spot is located at the center of the display interface, it indicates that the sample to be measured has been adjusted to a state horizontal with respect to the autocollimator 6. When the light spot is not located at the center of the display interface, it is necessary to separately adjust the three pen-shaped motors inside the stage until the light spot is at the center position. When calibrating the incident angle and the 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 by the autocollimator 6 is reflected at a specific angle after passing through the high-precision prism. When passing through the polarizer arm or the analyzer arm after reflection, it is reflected back by the lens on the polarizer arm or the analyzer arm. On the display interface of the autocollimator 6, when the light spot is located at the center of the display interface, it indicates that the calibration of the incident angle and the reflection angle is completed. When the light spot is not located at the center of the display interface, it is necessary to adjust the angle of the internal optical path of the polarizer arm and the analyzer arm until the light spot is at the center position.

[0047] In practical applications, the three polarizer arms need to be calibrated to the same state before installation. Specifically, use the same polarization tester to detect the light emitted by the polarizer arms. The polarizer arms are directly aligned with the same polarization tester. When the polarization brushless motors in the three polarizer arms are adjusted to the same angle, if the deviation between the polarization angles displayed in the polarization tester does not exceed 0.5%, it is determined that the calibration of the initial states of the three polarizer arms is completed.

[0048] In practical applications, the included angles between the fast axes of the phase retarders inside the first polarizer arm 1 and the second polarizer arm 2 and the polarization direction of the laser in propagation are equal. Specifically, use the same laser and polarizer to generate linearly polarized light with the same polarization angle. These two phase retarders will change the linearly polarized light into elliptically polarized light. When the deviation between the ellipticities measured by the two beams of elliptically polarized light does not exceed 0.5%, it indicates that the calibration of the two phase retarders is completed.

[0049] In practical applications, the three analyzer arms also need to be calibrated to the same state before installation. Specifically, use the linearly polarized light emitted by the same polarizer arm. The same polarizer arm is directly aligned with the three analyzer arms respectively. When the deviation between the parameters displayed by the polarization testers in all analyzer arms and the angles displayed by the analyzer brushless motors does not exceed 0.5%, it is determined that the calibration of the initial states of the three analyzer arms is completed.

[0050] In practical applications, the polarizer arm III 3 and the analyzer arm III 9 are in a coincident state in the horizontal direction and are symmetric with respect to the instrument central axis. This set of double-arm structures is used to measure the initial state of polarization. The internal optical path is that the helium-neon laser 13 emits linearly polarized light, which becomes linearly polarized light with a certain polarization angle after passing through the polarizer. During this process, it is measured by the polarization tester in the analyzer arm. When the linearly polarized angle in the display interface of the polarization tester is 0 degree, it indicates the state is the initial polarization state, and the rotation angle shown by the polarization brushless motor in this state is the initial polarization angle.

[0051] In practical applications, the polarizer arm II 2 and the analyzer arm II 8, and the polarizer arm III 3 and the analyzer arm III 9 are symmetric with respect to the instrument central axis. The functions of these two sets of double-arm structures are to measure the polarization state and the analyzer state when the incident angle is 45 degrees and 70 degrees. The internal optical path is that the helium-neon laser 13 emits linearly polarized light, which 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 retarder. The circularly polarized light becomes elliptically polarized light after being reflected by the sample surface. At this time, adjust the polarizer motor. After rotating a certain angle, the reflected elliptically polarized light is changed back to linearly polarized light. During this process, the rotation angle of the polarization brushless motor is the polarization angle, which is represented in the algorithm as the angle of the polarization brushless motor after adjustment minus the initial angle of the polarization brushless motor. The polarization angle of the linearly polarized light detected later by the polarization tester is the analyzer angle.

[0052] The polarization angle and the analyzer angle measured when the incident angle is 70 degrees are mainly used to calculate the thickness of the film outside the period. The polarization angle and the analyzer angle measured when the incident angle is 45 degrees are mainly used to calculate the number of film thickness periods. Specifically, combined with the parameters of the incident angle of 70 degrees, a unary unknown equation is established, and the number of thickness periods can be obtained by solving the equation. After obtaining the number of thickness periods and the thickness outside the period, use the formula D = n*T + d, where D is the total thickness of the film, n is the number of periods, T is the period thickness, and d is the thickness outside the period.

[0053] In the present invention, specific examples are used to elaborate the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An extinction ellipsometer, characterized in that: include: Base; The wafer stage is arranged on the base, used to absorb and fix the sample to be tested, and can drive the sample to be tested to move in multiple dimensions; A mounting frame is fixedly mounted on the base, and one side of the mounting frame is evenly provided with a plurality of obliquely arranged polarizing arms, and the other side is provided with a plurality of analyzing arms corresponding to the polarizing arms one by one; the polarizing arms and the corresponding analyzing arms are used to measure the ellipsometric parameters of the sample to be measured at different incident angles; The autocollimator is arranged on the mounting frame and is located directly above the wafer stage, and is used to correct the levelness of the surface of the sample to be tested.

2. The extinction ellipsometer according to claim 1, characterized in that: The polarizing arm comprises a coaxially arranged laser source, a polarizing brushless motor, a polarizing plate, and a phase retarder. The laser source is used to generate linearly polarized light. The polarizing brushless motor is provided with a polarizing plate on its rotating shaft. During the rotation of the polarizing brushless motor, the surface of the polarizing plate is always perpendicular to the propagation direction of the linearly polarized light. After the linearly polarized light passes through the polarizing plate, a first linearly polarized light with a determined polarization angle is generated. The phase retarder can convert the first linearly polarized light into circularly polarized light and irradiate the circularly polarized light onto a sample to be tested.

3. The extinction ellipsometer according to claim 1, characterized in that: The polarization analyzer arm comprises a polarization brushless motor, a polarization analyzer, a non-polarization beam splitter, a polarization tester and a photodetector. The polarization analyzer is arranged on the rotating shaft of the polarization brushless motor. The polarization brushless motor, the polarization analyzer and the photodetector are arranged coaxially. The light emitted by the polarization arm can be received by the polarization analyzer arm after being reflected by the surface of the sample to be tested, and enters the non-polarization beam splitter as the second linear polarized light. The non-polarization beam splitter splits the second linear polarized light into two, one beam is emitted into the polarization tester, and the other beam enters the photodetector after passing through the polarization brushless motor and the polarization analyzer.

4. The extinction ellipsometer according to claim 2, characterized in that: The laser source comprises a helium-neon laser, and each of the polarizing arms is provided with a helium-neon laser.

5. The extinction ellipsometer according to claim 2, characterized in that: Three polarizing arms are provided on one side of the mounting frame, the laser source includes a helium-neon laser, the helium-neon laser 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, and the first optical fiber, the third optical fiber and the fourth optical fiber are respectively connected to the three polarizing arms.

6. The extinction ellipsometer according to claim 2, characterized in that: Three polarizing arms are provided on one side of the mounting frame. The laser source includes a helium-neon laser. The laser emitted by the helium-neon laser is divided into a first laser beam and a second laser beam by a beam splitter. The second laser beam is divided 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 enters the second polarizing arm after being reflected by a reflector, and the fourth laser beam enters the third polarizing arm after being reflected by two reflectors.

7. The extinction ellipsometer according to claim 1, characterized in that: The mounting frame includes two arches symmetrically arranged on the base, the two arches are fixedly connected by a connecting block, and the bottom of the connecting block is fixedly connected to the base; the autocollimator is fixedly arranged on the top of the two arches; a measuring arm mounting base is provided on the side wall of the arch, and the polarizing arm and the analyzing arm are both installed on the measuring arm mounting seat.

8. The extinction ellipsometer according to claim 2, characterized in that: The phase retarder is arranged concentrically with the polarizing plate; 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 45 degrees to the polarization direction of the first linearly polarized light.

9. The extinction ellipsometer according to claim 7, characterized in that: The arch includes an arched portion, which is in a semicircular shape. A column with a rectangular cross-section is connected to the bottom of the arched portion, and the bottom of the column is connected to the base. The two arched portions are arranged concentrically, and the distance between the two arches is 400 mm.

10. The extinction ellipsometer according to claim 1, characterized in that: The wafer stage can achieve horizontal movement of the sample to be tested within a range of 300mm×300mm, 10mm vertical lifting and lowering, and full-range ±2° pitch.

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