Multi-channel micro-area angle-resolved monitoring system and monitoring method

Abstract

This invention relates to a multi-channel micro-area angle-resolved monitoring system and method. The monitoring system includes: a relatively movable incident arm and a receiving arm, the incident arm having at least two incident channels and the receiving arm having at least two receiving channels; an ellipsoidal beam path assembly and a holographic interference beam path assembly selectively and positionally adjustable in the incident and receiving channels; and a light source, a photodetector, and a large numerical aperture lens arranged in coordination. The ellipsoidal beam path assembly can be used to measure the ellipsoidal deviation of the sample, and the holographic interference beam path assembly can be used to perform off-axis digital holographic measurement of the sample. Furthermore, the relative movement of the incident arm and the receiving arm, combined with the large numerical aperture lens, allows for adjustment of the incident angle of the incident beam, thereby acquiring more comprehensive multi-dimensional optical signals and more accurately monitoring the optical properties of the sample.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device manufacturing and processing, and in particular to a multi-channel micro-area angle-resolved monitoring system and monitoring method. Background Technology

[0002] Semiconductor manufacturing is the foundation of the modern electronics and information industry, with micro-nano fabrication technology at its core. Deposition and etching are two crucial steps in micro-nano fabrication, playing a vital role in the manufacturing of current integrated circuits, optoelectronic devices, and other (thin-film) devices. The performance indicators of these devices are directly determined by the precision of these two processes. Furthermore, as semiconductor device sizes shrink and integration scales increase, the precision requirements for deposition and etching become increasingly stringent. This necessitates real-time monitoring of the deposition and etching progress to achieve high-precision control of both processes and meet desired device specifications. This explains why, although high-resolution imaging equipment such as scanning electron microscopes (SEM) and atomic force microscopes (AFM) provide precise morphological information and are widely used for semiconductor process yield inspection, they cannot be applied to real-time processing monitoring due to issues with inspection efficiency and environmental stability. Therefore, optical methods are typically employed to achieve real-time and efficient monitoring of these two processes.

[0003] Since deposition and etching are forward and reverse processes, respectively, the following discussion focuses on etching. To precisely control the etching depth, real-time monitoring is typically required during the etching process to determine the etching endpoint—this is known as etching endpoint detection. Currently, widely used etching endpoint detection systems include interferometric endpoint detection (IEP) and optical emission spectroscopy (OES). IEP is based on the principle of thin-film interference; as the etching depth changes, the interference pattern of the reflection spectrum also changes. By recording the changes in the spectrum at a specific wavelength over time, the etching rate and etching thickness can be calculated, thereby controlling the etching endpoint. OES is commonly used in ion beam etching, detecting the etching endpoint by monitoring the spectral characteristics of specific chemical groups or atoms in the plasma generated during the etching process.

[0004] However, while the aforementioned monitoring methods can control the etching depth relatively accurately, they all neglect the potential changes in refractive index during the etching process. Although refractive index is not a primary concern in the etching of integrated circuit devices, it is a crucial parameter in the etching of optoelectronic devices (such as photonic crystals and diffractive waveguides). Etching can easily induce changes in the material's refractive index, thereby affecting the device's optical performance. Therefore, not only the depth changes during etching (determining the etching endpoint) but also the potential changes in refractive index during etching are of great concern.

[0005] Currently, while there are monitoring devices for real-time acquisition of film thickness and refractive index during the etching process—namely, spectroscopic reflectometry (SR)—SR acquires the sample reflectance spectrum information at different wavelengths and uses numerical fitting to obtain film thickness and refractive index information. However, this monitoring method has drawbacks. The optical information acquired in a single measurement is very limited (e.g., only single polarization, single angle, etc.), resulting in high uncertainty in the film thickness and refractive index information obtained through numerical fitting. Furthermore, this method can only measure isotropic materials, limiting its application in sample preparation and testing for optoelectronics and condensed matter physics. Therefore, higher requirements are placed on real-time monitoring during the etching process. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides a multi-channel micro-area angle-resolved monitoring system and method, which can acquire more comprehensive optical signals across multiple dimensions, thereby enabling more accurate monitoring of the optical properties of samples.

[0007] This invention is achieved through the following scheme: a multi-channel micro-area angle-resolved monitoring system, comprising:

[0008] A monitoring box is provided with a monitoring cavity. Two moving stages are installed on the top surface of the monitoring box. The two moving stages are located on both sides of the central axis of the monitoring cavity. The bottom surface of the monitoring box is provided with an open or transparent window for aligning the sample processing area.

[0009] The cantilever assembly includes an incident arm and a receiving arm that extend vertically into the monitoring cavity and are respectively mounted on two moving platforms. The incident arm and the receiving arm achieve horizontal relative movement with respect to the central axis of the monitoring cavity through the two moving platforms. The incident arm is divided into at least two incident channels by a first partition, and the receiving arm is divided into at least two receiving channels by a second partition. The first partition has a first connecting port for connecting two adjacent incident channels, and the second partition has a second connecting port for connecting two adjacent receiving channels. A retractable channel is also connected between the relatively close incident channels and receiving channels.

[0010] The measurement module includes a light source for emitting an incident beam into an incident channel, a photodetector for receiving a beam emitted from a receiving channel, a large numerical aperture lens for focusing the incident beam onto the sample processing area and directing the reflected beam from the sample into the receiving channel, an ellipsometric optical path assembly for ellipsometric measurement of the sample, and a holographic interference optical path assembly for off-axis digital holographic measurement of the sample. The light source and the photodetector are respectively mounted on two moving stages, and the moving stages achieve synchronous movement with the incident arm and the receiving arm, respectively. The optical elements in the ellipsometric optical path assembly and the holographic interference optical path assembly are selectively and positionably arranged in the incident channel and the receiving channel, respectively. The large numerical aperture lens is mounted between the cantilever assembly and the opening or transparent window.

[0011] A further improvement of the multi-channel micro-area angle resolution monitoring system of the present invention is that: the number of incident channels and the number of receiving channels are both two; the retractable channel is connected to the upper part of the inner incident channel and the inner receiving channel; the first connecting port is located below the retractable channel; and the second connecting port is directly opposite the retractable channel.

[0012] The light source is connected to the inner incident channel, and the photodetector includes a photomultiplier tube and a camera. The photomultiplier tube is connected to the inner receiving channel, and the camera is positioned opposite the outer receiving channel.

[0013] The elliptic polarization path assembly is arranged in the inner incident channel and the inner receiving channel;

[0014] The holographic interference optical path assembly includes a first beam splitter and a second beam splitter respectively disposed in the inner incident channel and the outer receiving channel and both facing the retractable channel, a third beam splitter and a reflector respectively disposed in the inner incident channel and the outer incident channel and both facing the first communication port, and a first lens and a second lens respectively and symmetrically disposed at the lower positions in the outer incident channel and the outer receiving channel.

[0015] A further improvement of the multi-channel micro-area angle resolution monitoring system of the present invention is that: there are two incident channels and two receiving channels; the retractable channel is connected to the upper part of the inner incident channel and the inner receiving channel; and the first connecting port and the second connecting port are both set directly opposite the retractable channel.

[0016] The light source has two components, which are respectively connected to the inner incident channel and the outer incident channel. The photodetector includes a photomultiplier tube and a camera. The photomultiplier tube is connected to the inner receiving channel, and the camera is positioned opposite the outer receiving channel.

[0017] The elliptic polarization path assembly is arranged in the inner incident channel and the inner receiving channel;

[0018] The holographic interference optical path assembly includes a first beam splitter and a second beam splitter respectively disposed in the outer incident channel and the outer receiving channel and both facing the retractable channel, and a first lens and a second lens respectively and symmetrically disposed at the lower positions in the outer incident channel and the outer receiving channel.

[0019] A further improvement of the multi-channel micro-area angle-resolved monitoring system of the present invention is that the elliptic polarization path assembly includes a polarizer and two first photoelastic modulators arranged from top to bottom in the inner incident channel, and an analyzer and two second photoelastic modulators arranged from top to bottom in the inner receiving channel.

[0020] A further improvement of the multi-channel micro-area angle-resolved monitoring system of the present invention is that: the elliptic polarization path assembly includes a polarizer and a first compensator disposed from top to bottom in the inner incident channel, and a polarizer and a second compensator disposed from top to bottom in the inner receiving channel; wherein the first compensator and the second compensator are rotatably mounted in the inner incident channel and the inner receiving channel, respectively.

[0021] A further improvement of the multi-channel micro-area angle resolution monitoring system of the present invention is that the elliptic polarization path assembly includes a polarizer, a first liquid crystal sheet, a first wave plate and a first liquid crystal sheet arranged from top to bottom in the inner incident channel, and an analyzer, a second liquid crystal sheet, a second wave plate and a second liquid crystal sheet arranged from top to bottom in the inner receiving channel.

[0022] A further improvement of the multi-channel micro-area angle-resolved monitoring system of the present invention is that the holographic interference optical path assembly further includes two lens groups for realizing achromatic and microscopic functions. The two lens groups are detachably installed in the outer incident channel and the outer receiving channel, respectively, and are located above the first lens and the second lens.

[0023] A further improvement of the multi-channel micro-area angle-resolved monitoring system of the present invention is that the measurement module further includes a microscope assembly detachably mounted between the cantilever assembly and the large numerical aperture lens.

[0024] This invention also provides a multi-channel micro-area angular resolution monitoring method:

[0025] Provide a multi-channel micro-area angle-resolved monitoring system as described in any of the preceding claims, and mount the monitoring box above the sample processing area so that the opening or transparent window faces the sample processing area;

[0026] During sample processing, an incident beam is emitted into the incident channel using a light source, and the ellipsometrics of the sample is measured in real time using an ellipsometric optical path assembly to obtain the Mueller matrix information of the sample. A holographic interference optical path assembly is then used to perform off-axis digital holographic measurements of the sample in real time to obtain the phase information of the sample.

[0027] During real-time ellipsometric measurement and off-axis digital holographic measurement, two moving stages are used to drive the incident arm and the receiving arm to move horizontally along the central axis of the monitoring cavity, so as to change the incident angle when the incident beam enters the sample processing area, thereby obtaining the Mueller matrix information and phase information of the sample corresponding to the incident beam at different angles.

[0028] A further improvement of the multi-channel micro-area angle-resolved monitoring method of the present invention is that the sample processing process is a deposition process or an etching process. During the sample processing, Mueller matrix information and phase information at different angles are acquired in units of one measurement cycle. The optical properties of the sample under different measurement cycles are analyzed based on the Mueller matrix information and phase information at different angles. The optical properties include the film thickness, refractive index and surface morphology of the sample.

[0029] This invention includes, but is not limited to, the following beneficial effects:

[0030] 1. By combining ellipsometric measurement and off-axis digital holographic measurement, multi-dimensional optical signals with multiple wavelengths, angles, and polarization states can be acquired simultaneously within one measurement cycle under a single light source. This provides more comprehensive optical information, enabling more accurate acquisition of optical properties such as film thickness, refractive index, and phase of samples under different measurement cycles. Compared with traditional monitoring methods, this method offers higher accuracy and more comprehensive information.

[0031] 2. Through the interconnected design of the multi-channel, connecting port, and retractable channel of the cantilever assembly, as well as the cooperation of optical elements such as beam splitters, at least two measurements can be achieved using a single light source. Furthermore, different measurement methods can be integrated while also being separated from each other, avoiding crosstalk between different optical information.

[0032] 3. By using lenses with large size and large numerical aperture, light rays incident from different positions can be converged and formed into oblique incident light at different angles, thereby achieving angle-resolved measurement and providing a new angle-resolved measurement mode.

[0033] 4. Micro-area measurements of samples can be achieved through large numerical aperture lenses and optional microscope arrays, avoiding interference from optical information in irrelevant areas. Attached Figure Description

[0034] Figure 1 A cross-sectional elevation view of an embodiment of the multi-channel micro-area angle-resolved monitoring system of the present invention is shown.

[0035] Figure 2 A cross-sectional elevation view of another embodiment of the multi-channel micro-area angle-resolved monitoring system of the present invention is shown.

[0036] Figure 3 The Mueller matrix diagram obtained by ellipsometric measurement of a sample using the present invention is shown.

[0037] Figure 4 The phase map obtained by off-axis digital holographic measurement of a sample using the present invention is shown.

[0038] Figure 5 The diagram shows the phase image obtained by off-axis digital holographic measurement of a sample without the microscope module installed according to the present invention. Detailed Implementation

[0039] To address the limitations of traditional sample processing monitoring methods, which acquire limited optical information in a single measurement and can only measure isotropic materials, this invention provides a multi-channel micro-area angle-resolved monitoring system and method. This system can acquire more comprehensive, multi-dimensional optical signals, thereby enabling more accurate monitoring of the optical properties of samples. The following detailed description, in conjunction with the accompanying drawings, provides further insights into this multi-channel micro-area angle-resolved monitoring system and method.

[0040] See Figure 1 and Figure 2As shown. A multi-channel micro-area angle-resolved monitoring system includes: a monitoring box 1 with a monitoring cavity, wherein two moving stages 11 and 12 are mounted on the top surface of the monitoring box 1, preferably driven by stepper motors respectively. The two moving stages 11 and 12 are located on both sides of the central axis of the monitoring cavity. The bottom surface of the monitoring box 1 is provided with a transparent window 13 for aligning the sample processing area to allow the light beam to pass through. Correspondingly, the sample processing area is usually enclosed in a processing cavity 2. To facilitate the light beam to pass between the monitoring box 1 and the processing cavity 2, a transparent window 21 is also provided on the top surface of the processing cavity 2. During monitoring, the monitoring box 1 is placed above the processing cavity 2, with the two transparent windows facing each other. The cantilever assembly includes an incident arm 21 and a receiving arm 22 that extend vertically into the monitoring cavity and are respectively mounted on two moving platforms 11 and 12. The incident arm 21 and the receiving arm 22 achieve horizontal relative movement with respect to the central axis of the monitoring cavity through the two moving platforms 11 and 12. Both the incident arm 21 and the receiving arm 22 are hollow structures. The incident arm 21 is divided into at least two incident channels by a first partition 211, and the receiving arm 22 is divided into at least two receiving channels by a second partition 221. The first partition 221 has a first connecting port for connecting two adjacent incident channels, and the second partition 221 has a second connecting port for connecting two adjacent receiving channels. A retractable channel 23, which can be a corrugated pipe, is also connected between relatively close incident channels and receiving channels. The retractable channel 23 allows for synchronous adjustment of its length when the moving platforms move. The measurement module includes a light source for emitting an incident beam to an incident channel, a photodetector for receiving a beam emitted from a receiving channel, a large numerical aperture lens 32 for focusing the incident beam to the sample processing area and directing the reflected beam reflected from the sample into the receiving channel, an ellipsometric optical path assembly for performing ellipsometric measurements on the sample, and a holographic interference optical path assembly for performing off-axis digital holographic measurements on the sample. The light source is a source that can provide highly coherent, multi-wavelength light. It can be a broadband high-coherence white light source or a broadband laser. The light source is connected to the incident arm 21 via an optical fiber and is installed on the corresponding moving stage. The photodetector includes a photomultiplier tube (PMT) and a CCD camera 31 for collecting beam information, as well as a computer processing device connected to the PMT and CCD camera for processing beam information. The PMT is connected to the receiving arm 22 via an optical fiber, and both the PMT and CCD camera 31 are installed on the corresponding moving stage. The light source and photodetector move synchronously with the incident arm 21 and the receiving arm 22 via two moving stages 11 and 12, respectively. The optical elements in the ellipsoidal polarization path assembly and the holographic interference path assembly are selectively and positionally arranged in the incident channel and the receiving channel. The large numerical aperture lens 32 is installed between the cantilever assembly and the transparent window 13.

[0041] This monitoring system can perform ellipsometric measurements on samples using an ellipsometric optical path component and off-axis digital holographic measurements using a holographic interference optical path component. Furthermore, by adjusting the incident angle of the incident beam through the relative movement of the incident and receiving arms and in conjunction with a large numerical aperture lens, it can acquire more comprehensive, multi-dimensional optical signals and more accurately monitor the optical properties of the samples. The principles of ellipsometric measurement and off-axis digital holographic measurement are explained below. The ellipsometric measurement section utilizes the Mueller matrix to describe the transmission of optical information, thereby comprehensively acquiring the sample's properties. The Mueller matrix, a 4×4 matrix, describes the change in light polarization state, essentially defined by Stokes parameters. Stokes parameters are four quantities describing the light polarization state, denoted by S0, S1, S2, and S3. These four quantities comprehensively describe the polarization state of light using the total light intensity and the intensity difference between different polarization states. They can describe not only fully polarized light but also unpolarized or partially polarized light, containing a wealth of optical information. In optical detection, the unique properties of a sample are often encompassed by the polarization conversion of light. Therefore, by acquiring the Mueller matrix information of the sample, optical properties such as film thickness, refractive index, and optical rotation can be extracted. For many samples in the optical field, their surface phase distribution is crucial information. Therefore, this monitoring system incorporates off-axis digital holographic measurement technology to simultaneously and efficiently acquire the sample phase. This off-axis digital holographic measurement utilizes the principle of optical interference. A reference beam with a certain angle to the optical axis is drawn from the incident beam and interfered with the object beam reflected from the sample. The resulting interference pattern is then used to invert the relative phase information and three-dimensional morphology of the sample surface, revealing optical characteristics such as the uniformity of the sample surface.

[0042] The ellipsometric optical path component and the holographic interference optical path component used to realize ellipsometric measurement and off-axis digital holographic measurement respectively can be flexibly configured according to the specific structure of the incident arm 21 and the receiving arm 22. Two preferred embodiments are provided below:

[0043] Example 1: As Figure 1As shown, the incident arm 21 is divided into two incident channels by a vertical first partition 211, and the receiving arm 22 is divided into two receiving channels by a vertical second partition 221. The retractable channel 23 connects the upper part of the inner incident channel (i.e., the side near the central axis of the monitoring cavity) and the inner receiving channel (i.e., the side near the central axis of the monitoring cavity). The first connecting port on the first partition 211 is located below the retractable channel 23, and the second connecting port on the second partition 221 is directly opposite the retractable channel 23. A fiber optic incident port 61 is provided on the mobile stage 11 connected to the incident arm 21 at a position corresponding to the inner incident channel. A 10-band broadband high coherence light source (covering light from ultraviolet to near-infrared wavelengths, typically in the 200nm to 2000nm band) is connected to the fiber optic incident port 61 through an optical fiber. The mobile stage 12, connected to the receiving arm 22, has a first fiber optic exit port 62 and a second fiber optic exit port 63 at positions corresponding to the inner and outer receiving channels, respectively. A photomultiplier tube (PMT) is connected to the first fiber optic exit port 62 via a polarization-maintaining fiber, and a CCD camera is connected to the second fiber optic exit port 63. The ellipsometric path assembly includes, from top to bottom, a polarizer 41 (i.e., a polarization modulator or polarizer) and two first photoelastic modulators 42 and 43 (photoelastic modulators are also called electro-optic modulators, which can change the birefringence of the crystal within them according to the applied voltage, thereby changing the phase difference between the two orthogonal components of the transmitted polarized light), and, from top to bottom, an analyzer 46 (of the same specifications as the polarizer 41) and two second photoelastic modulators 44 and 45, all located within the inner receiving channel. In this embodiment, the inner incident channel and the inner exit channel serve as the ellipsometric measurement incident arm and the ellipsometric measurement receiving arm, respectively, so that the measured angular-resolved spectrum covers small-angle information. The holographic interference optical path assembly includes a first beam splitter 51 and a second beam splitter 52 respectively disposed in the inner incident channel and the outer receiving channel and both facing the retractable channel 23, a third beam splitter 53 and a reflector 54 respectively disposed in the inner incident channel and the outer incident channel and both facing the first communication port, and a first lens 55 and a second lens 56 respectively and symmetrically disposed at the lower positions in the outer incident channel and the outer receiving channel.

[0044] When performing ellipsometric measurements using the aforementioned ellipsometric optical path assembly, an incident beam emitted from the light source is transmitted via optical fiber and coupled into the inner incident channel through the optical fiber incident port 61. After passing through the first beam splitter 51, the incident beam reaches the polarizer 41. At this point, the angle of the polarizer 41 is fixed to generate a polarized beam with a specific polarization. This polarized beam then passes through the first photoelastic modulators 42 and 43, which are set at specific angles, to generate a modulated beam whose polarization characteristics change over time, providing different polarization information. This modulated beam is focused onto the sample after passing through the large numerical aperture lens 32, and then, after reflection from the sample and refraction by the large numerical aperture lens 32, enters the inner receiving channel of the receiving arm 22. The reflected beam, after entering the inner receiving channel, passes sequentially through the second photoelastic modulators 44 and 45 and the analyzer 46 before being coupled out through the first optical fiber exit port 62. After passing through the polarization-maintaining fiber, it is received by the photomultiplier tube (PMT). The phase delays of the first photoelastic modulators 42 and 43 and the second photoelastic modulators 44 and 45 are controlled by the corresponding controllers and power supply circuits. Meanwhile, the angle settings of the second photoelastic modulators 44 and 45 are the same as those of the first photoelastic modulators 43 and 42, respectively, to ensure that all 16 Mueller matrix elements can be measured during the ellipsometry measurement process.

[0045] When performing off-axis digital holographic measurements using the aforementioned holographic interference optical path assembly, it is necessary to acquire a reference beam and an object beam reflected from the sample to form an interference pattern, thereby resolving the three-dimensional morphology of the sample surface. The acquisition of the reference beam is as follows: a portion of the beam entering the fiber optic input port 61 is reflected by the first beam splitter 51, passes through the retractable channel 23, reaches the holographic measurement receiving arm (i.e., the outer receiving channel), and is then reflected by the tilted second beam splitter 52 (since off-axis digital holography requires the introduction of a certain tilt angle in the reference beam, the second beam splitter 52 can be angled for adjustment), forming a beam with a certain tilt angle, which is then received by the second fiber optic output port 63. The object beam is acquired as follows: A portion of the beam passing through the first beam splitter 51 is reflected at the third beam splitter 53 and enters the interferometric measurement incident arm (i.e., the outer incident channel). After being reflected by the mirror 54, the beam is converged by the first lens 55 and then refracted by the large numerical aperture lens 32 to form a parallel beam that illuminates the sample. The object beam reflected by the sample passes again through the large numerical aperture lens 32 and the second lens 56 (of the same specifications as the first lens 55), and then passes through the second beam splitter 52 along the same path. Finally, it is received by the second fiber optic output port 63. The object beam and the reference beam interfere on the surface of the CCD camera 31 through the second fiber optic output port 63. The acquired optical signal is converted by photoelectric conversion and processed by a computer to obtain the phase distribution of the object surface, thereby obtaining the three-dimensional surface structure.

[0046] Considering that phase measurements typically use monochromatic light for interference, filtering is necessary. Therefore, in this embodiment, a filter 57 (i.e., a light filter) is also provided between the second fiber optic output port 63 and the second beam splitter 52 to filter out light of a specific wavelength. This embodiment, through the interconnected design of the cantilever assembly's multi-channel, connecting ports, and retractable channels, as well as the cooperation of optical elements such as beam splitters, enables at least two measurements to be achieved using a single light source. Furthermore, it allows for the fusion of different measurement methods while simultaneously separating them, avoiding crosstalk between different optical information.

[0047] Example 2: Figure 2 As shown, the main difference between this embodiment and Embodiment 1 lies in the arrangement of the connection port, the light source, and the holographic interference optical path assembly. Specifically: the first connection port on the first partition 211 and the second connection port on the second partition 221 are both positioned directly opposite the retractable channel 23; the moving stage 11 connected to the incident arm 21 has a first fiber optic incident port 60 at the position corresponding to the outer incident channel and a second fiber optic incident port 61 at the position corresponding to the inner incident channel; the light source is a dual light source, including a monochromatic laser light source and a broadband white light light source; the monochromatic laser light source is connected to the first fiber optic incident port 60 via a single-mode fiber, and the broadband white light source is connected to the second fiber optic incident port 61 via an optical fiber; the holographic interference optical path assembly includes a first beam splitter 51 and a second beam splitter 52 respectively disposed in the outer incident channel and the outer receiving channel and both directly opposite the retractable channel 23, and a first lens 55 and a second lens 56 respectively and symmetrically disposed at the lower positions in the outer incident channel and the outer receiving channel.

[0048] The principle of ellipsometry measurement using the ellipsometry optical path component in this embodiment is the same as that in Embodiment 1, and will not be repeated here.

[0049] When performing off-axis digital holographic measurement using the holographic interference optical path assembly of this embodiment, the reference light is acquired as follows: A beam emitted from a monochromatic laser source is coupled into the holographic measurement incident arm (i.e., the outer incident channel) through a single-mode fiber and the first fiber incident port 60. It is then split into two beams by the first beam splitter 51. One beam passes through the retractable channel 23 to the holographic measurement receiving arm (i.e., the outer receiving channel), and is reflected by the tilted second beam splitter 52 to form a beam with a certain tilt angle, which is then received by the second fiber exit port 63. The object light is acquired as follows: The other beam, split by the first beam splitter 51, passes through the first lens 55 along its original path and converges. It is then refracted by the large numerical aperture lens 32 to form a parallel beam that illuminates the sample. The object light reflected from the sample passes again through the large numerical aperture lens 32 and the second lens 56, and passes through the second beam splitter 52 along its original path, finally being received by the second fiber exit port 63. The object light and the reference light interfere on the surface of the CCD camera 31 through the second fiber optic output port 63. The acquired optical signals are converted by photoelectric conversion and processed by computer to obtain the phase distribution of the object surface, thereby obtaining the three-dimensional surface structure.

[0050] This embodiment uses a separate light source (i.e., a monochromatic laser light source) for off-axis digital holographic measurement, which simplifies the configuration of optical elements in the holographic interference optical path assembly. Furthermore, through the interconnected design of the multi-channel, connecting port, and retractable channel of the cantilever assembly, as well as the cooperation of optical elements such as beam splitters, different measurement methods can be integrated while also being separated from each other, avoiding crosstalk between different optical information.

[0051] The elliptic polarization path components in the two embodiments described above can also be replaced by the following alternatives:

[0052] Example 3: The two first photoelastic modulators 42 and 43, and the two second photoelastic modulators 44 and 45 can be replaced with a compensator (or a delay plate). At the same time, when performing elliptic measurement, the two compensators can be controlled to rotate in the same direction according to a certain rotation speed ratio. The 16 elements of the Mueller matrix can also be obtained, thereby fitting and obtaining the corresponding optical parameters.

[0053] Example 4: The two first photoelastic modulators 42 and 43, and the two second photoelastic modulators 44 and 45 can be replaced with modules composed of a liquid crystal panel, a waveplate and a liquid crystal panel of the same specification in sequence.

[0054] To achieve achromatic and microscopic functions and enrich the functionality of the monitoring system, Embodiment 5 is provided: several 4f lens groups can be optionally mounted above the first lens 55 and the second lens 56 in any of the above embodiments.

[0055] To enable measurements of smaller areas of the sample, Embodiment Six is ​​provided: a microscope assembly can be installed between the cantilever assembly (which may only cover the ellipsometric measurement incident and receiving arm ranges) and the large numerical aperture lens 32 in any of the above embodiments. The microscope assembly allows for targeted measurements of the desired small areas, such as measuring only the etched area of ​​the sample, eliminating spectral interference from non-etched areas.

[0056] A multi-channel micro-area angular resolution monitoring method includes the following steps:

[0057] Step 1: Provide a multi-channel micro-area angle-resolved monitoring system as described in any of the above, and set up the monitoring system 1 above the sample processing area (i.e., the processing cavity 2), so that the transparent window 13 is directly facing the sample processing area;

[0058] Step 2: During the sample processing (which may be the sample deposition process or etching process), an incident beam is emitted into the incident channel using a light source, and the ellipticization of the sample is measured in real time using an ellipticization optical path component to obtain the Mueller matrix information of the sample. The sample is then measured in real time using a holographic interference optical path component to obtain the phase information of the sample.

[0059] It should be noted that ellipsometric measurement and off-axis digital holographic measurement can be performed continuously and alternately to obtain real-time measurement results, and the two measurement methods do not interfere with each other. Furthermore, during sample processing, Mueller matrix information and phase information at different angles can be acquired in units of one measurement cycle. Based on the acquired Mueller matrix information and phase information at different angles, the optical properties of the sample under different measurement cycles can be analyzed. These optical properties include information such as the sample's film thickness, refractive index, and surface morphology. Specifically, during real-time ellipsometric measurement and off-axis digital holographic measurement, two moving stages drive the incident arm and receiving arm to move horizontally along the central axis of the monitoring cavity. Beams incident at different axial positions are converged by the large numerical aperture lens 32 to form incident light at different angles. Typically, the same material will have different response characteristics to incident light at different angles. Therefore, this method can be used to perform angle-resolved measurements (i.e., collecting optical response signals at different angles), which can provide richer surface information. Then, using this multi-dimensional (including multi-angle, multi-wavelength, and multi-polarization) information, algorithms can be used for inversion to facilitate the analysis of more accurate optical properties, including information such as the film thickness, refractive index, and surface morphology of the sample.

[0060] This monitoring system was used to monitor the etching process of a 300 nm silicon film on a 500 μm silica substrate. In a specific etched area, the measured sample information was equivalent to the optical properties of the bilayer film. (See Figure 3.) Figure 3The Mueller matrix obtained from ellipsometry is shown, and the thickness was determined to be 299 nanometers after fitting algorithm. See also... Figure 4 As shown, Figure 4 The phase map obtained from off-axis digital holographic measurement is shown, exhibiting thin film phase characteristics. However, due to potential sample tilt and etching inhomogeneity, the phase distribution in this region shows a gradual change. The phase map without the microscope module does not display this gradual effect. Figure 5 As shown, Figure 5 The sample surface phase distribution obtained by off-axis digital holographic measurement without the microscope module is shown.

[0061] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A multi-channel micro-area angle-resolved monitoring system, characterized in that, include: A monitoring box is provided with a monitoring cavity. Two moving stages are installed on the top surface of the monitoring box. The two moving stages are located on both sides of the central axis of the monitoring cavity. The bottom surface of the monitoring box is provided with an open or transparent window for aligning the sample processing area. The cantilever assembly includes an incident arm and a receiving arm that extend vertically into the monitoring cavity and are respectively mounted on two moving platforms. The incident arm and the receiving arm achieve horizontal relative movement with respect to the central axis of the monitoring cavity through the two moving platforms. The incident arm is divided into at least two incident channels by a first partition, and the receiving arm is divided into at least two receiving channels by a second partition. The first partition has a first connecting port for connecting two adjacent incident channels, and the second partition has a second connecting port for connecting two adjacent receiving channels. A retractable channel is also connected between the relatively close incident channels and receiving channels. The measurement module includes a light source for emitting an incident beam into an incident channel, a photodetector for receiving a beam emitted from a receiving channel, a large numerical aperture lens for focusing the incident beam onto the sample processing area and directing the reflected beam from the sample into the receiving channel, an ellipsometric optical path assembly for ellipsometric measurement of the sample, and a holographic interference optical path assembly for off-axis digital holographic measurement of the sample. The light source and the photodetector are respectively mounted on two moving stages, and the moving stages achieve synchronous movement with the incident arm and the receiving arm, respectively. The optical elements in the ellipsometric optical path assembly and the holographic interference optical path assembly are selectively and positionably arranged in the incident channel and the receiving channel, respectively. The large numerical aperture lens is mounted between the cantilever assembly and the opening or transparent window.

2. The multi-channel micro-area angle-resolved monitoring system as described in claim 1, characterized in that: There are two incident channels and two receiving channels. The retractable channel is connected to the upper part of the inner incident channel and the inner receiving channel. The first connecting port is located below the retractable channel, and the second connecting port is directly opposite the retractable channel. The light source is connected to the inner incident channel, and the photodetector includes a photomultiplier tube and a camera. The photomultiplier tube is connected to the inner receiving channel, and the camera is positioned opposite the outer receiving channel. The elliptic polarization path assembly is arranged in the inner incident channel and the inner receiving channel; The holographic interference optical path assembly includes a first beam splitter and a second beam splitter respectively disposed in the inner incident channel and the outer receiving channel and both facing the retractable channel, a third beam splitter and a reflector respectively disposed in the inner incident channel and the outer incident channel and both facing the first communication port, and a first lens and a second lens respectively and symmetrically disposed at the lower positions in the outer incident channel and the outer receiving channel.

3. The multi-channel micro-area angle-resolved monitoring system as described in claim 1, characterized in that: The number of incident channels and receiving channels are both two. The retractable channel is connected to the upper part of the inner incident channel and the inner receiving channel. The first connecting port and the second connecting port are both set directly opposite the retractable channel. The light source has two components, which are respectively connected to the inner incident channel and the outer incident channel. The photodetector includes a photomultiplier tube and a camera. The photomultiplier tube is connected to the inner receiving channel, and the camera is positioned opposite the outer receiving channel. The elliptic polarization path assembly is arranged in the inner incident channel and the inner receiving channel; The holographic interference optical path assembly includes a first beam splitter and a second beam splitter respectively disposed in the outer incident channel and the outer receiving channel and both facing the retractable channel, and a first lens and a second lens respectively and symmetrically disposed at the lower positions in the outer incident channel and the outer receiving channel.

4. The multi-channel micro-area angle-resolved monitoring system as described in claim 2 or 3, characterized in that: The elliptic polarization path assembly includes a polarizer and two first photoelastic modulators arranged from top to bottom in the inner incident channel, and an analyzer and two second photoelastic modulators arranged from top to bottom in the inner receiving channel.

5. The multi-channel micro-area angle-resolved monitoring system as described in claim 2 or 3, characterized in that: The elliptic polarization path assembly includes a polarizer and a first compensator disposed from top to bottom in the inner incident channel, and an analyzer and a second compensator disposed from top to bottom in the inner receiving channel; wherein the first compensator and the second compensator are rotatably mounted in the inner incident channel and the inner receiving channel, respectively.

6. The multi-channel micro-area angle-resolved monitoring system as described in claim 2 or 3, characterized in that: The elliptic polarization path assembly includes, from top to bottom, a polarizer, a first liquid crystal panel, a first wave plate, and a first liquid crystal panel disposed in the inner incident channel, and from top to bottom, an analyzer, a second liquid crystal panel, a second wave plate, and a second liquid crystal panel disposed in the inner receiving channel.

7. The multi-channel micro-area angle-resolved monitoring system as described in claim 2 or 3, characterized in that: The holographic interference optical path assembly also includes two lens groups for achieving achromatic and microscopic functions. The two lens groups are detachably installed in the outer incident channel and the outer receiving channel, respectively, and are located above the first lens and the second lens.

8. The multi-channel micro-area angle-resolved monitoring system as described in claim 1, characterized in that: The measurement module also includes a microscope assembly detachably mounted between the cantilever assembly and the large numerical aperture lens.

9. A multi-channel micro-area angular resolution monitoring method, characterized in that: A multi-channel micro-area angle-resolved monitoring system as described in any one of claims 1 to 8 is provided, and the monitoring box is mounted above the sample processing area, with the opening or transparent window facing the sample processing area; During sample processing, an incident beam is emitted into the incident channel using a light source, and the ellipticization of the sample is measured in real time using an ellipticization optical path component to obtain the Mueller matrix information of the sample. The off-axis digital holographic measurement of the sample is performed in real time using a holographic interference optical path component to obtain the phase information of the sample. in During real-time ellipsometric measurement and off-axis digital holographic measurement, two moving stages are used to drive the incident arm and the receiving arm to move horizontally along the central axis of the monitoring cavity, so as to change the incident angle when the incident beam enters the sample processing area, thereby obtaining the Mueller matrix information and phase information of the sample corresponding to the incident beam at different angles.

10. The multi-channel micro-area angular resolution monitoring method as described in claim 9, characterized in that: The sample processing is a deposition process or an etching process. During the sample processing, Mueller matrix information and phase information at different angles are acquired in one measurement cycle. The optical properties of the sample under different measurement cycles are analyzed based on the acquired Mueller matrix information and phase information at different angles. The optical properties include information such as the film thickness, refractive index, and surface morphology of the sample.

Images