Etching gas monitoring system and gas state analysis method

Abstract

The present invention provides an etching gas monitoring system and a gas state analysis method. The system includes: a signal light source comb, a local oscillator light source comb, a light guide module, a plasma etching chamber, a first signal acquisition device, a reference arm, and a gas state analysis device. The light guide module combines signal light emitted by the signal light source comb and local oscillator light emitted by the local oscillator light source comb to obtain mixed light, and then splits the mixed light into detection light and reference light. The etching gas in the plasma etching chamber absorbs the detection light, and the first signal acquisition device converts the absorbed detection light into an etching radio frequency signal. The reference gas in the reference arm absorbs the reference light and converts the absorbed reference light into a reference radio frequency signal. The gas state analysis device is connected to the signal acquisition device and the reference arm, respectively, and determines the etching gas state based on the etching radio frequency signal and the reference radio frequency signal, thereby improving the sensitivity, resolution, and real-time performance of etching gas monitoring.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuit manufacturing, and in particular to an etching gas monitoring system and a gas state analysis method. Background Art

[0002] Plasma etching is a very important process technology for manufacturing semiconductor devices. The usual practice is to combine plasma etching with photolithography technology. The photolithography pattern obtained after plane exposure is used as a mask. The thin film material at a certain depth on the substrate surface is removed accurately and controllably through chemical reactions, auxiliary energy ions or electrons and pattern conversion, leaving the area that is not desired to be etched (i.e., the required processing pattern) to form etched features such as through holes and grooves. After etching the underlying material, ashing or stripping treatment is used to remove the remaining radiation-sensitive material from the substrate, exposing the etched structure for the next step of processing.

[0003] The processing of devices such as semiconductors often requires etching multiple material layers. Once an opening or pattern is formed in the upper material layer, the etching process must be accurately stopped. To control the etching process, various types of endpoint control are used. Endpoint control techniques typically rely on analyzing the chemical composition of the gases in the plasma etching chamber to infer whether the etching process has progressed to the underlying layer. During the process, the reactant and generated gases are in a plasma state, and particles at high energy levels transition to lower energy levels and radiate light. Different substances have different emission spectra with different wavelengths, and the spectral intensity is related to the density of the gases and the power used to generate the plasma. This type of spectrum is called optical emission spectroscopy (OES). Optical emission spectroscopy is currently the most commonly used endpoint detection method. It can sensitively detect subtle changes in the reaction, enabling real-time monitoring of the process and obtaining information on the chemical composition of the gases in the plasma processing chamber. The activated chemical species in the plasma optical emission spectrum produce different spectral characteristics. For example, the removal of the layer being etched and the exposure of the lower layer on the substrate will cause changes in the optical emission spectrum. The above changes can be used to accurately determine whether the upper layer etching is completed to terminate the etching process, avoid the lower layer from being etched or form other defects that lead to production failure.

[0004] The key to Moore's Law for integrated circuits is the continuous development of integrated circuit equipment technology. However, as the critical dimensions of advanced chips continue to shrink, stringent requirements are placed on the accuracy of the etching process, requiring control at the atomic level. Therefore, single-atom-level detection and control technology is required for online monitoring of manufacturing equipment. However, optical emission spectroscopy currently faces a significant bottleneck problem, because the signal intensity of optical emission spectroscopy is proportional to the number of gas atoms or molecules at high energy levels, and the number of particles at high energy levels is much smaller than the number of particles at low energy levels. As the process evolves, the etching rate is very slow or the etched area is very small, the corresponding reactant or product content is very low, and the number of particles at high energy levels is very small. The resulting optical emission spectrum signal intensity becomes weaker, and the signal intensity changes during the process are not obvious, which can easily lead to detection failure. Summary of the Invention

[0005] The main purpose of the embodiments of the present invention is to provide an etching gas monitoring system and a gas state analysis method to improve the sensitivity, resolution and real-time performance of etching gas monitoring.

[0006] To achieve the above objectives, an embodiment of the present invention provides an etching gas monitoring system, comprising:

[0007] A signal light source optical comb, a local oscillator light source optical comb, a light guide module, a plasma etching chamber, a first signal acquisition device, a reference arm, and a gas state analysis device;

[0008] The light guide module is used to combine the signal light emitted by the signal light source optical comb and the local oscillator light emitted by the local oscillator light source optical comb to obtain mixed light, and split the mixed light into detection light and reference light;

[0009] The etching gas in the plasma etching chamber is used to absorb the detection light, and the absorbed detection light is sent to the first signal acquisition device, so that the first signal acquisition device converts the absorbed detection light into an etching radio frequency signal;

[0010] The reference gas in the reference arm is used to absorb the reference light and convert the absorbed reference light into a reference radio frequency signal;

[0011] The gas state analysis device is connected to the signal acquisition device and the reference arm respectively, and is used to determine the etching gas state according to the etching radio frequency signal and the reference radio frequency signal.

[0012] In one embodiment, the light guide module includes a first reflector and a beam splitter;

[0013] The local oscillator light is reflected by the first reflector to the beam splitter;

[0014] The beam splitter is used to combine the signal light and the local oscillator light to obtain mixed light, and then split the mixed light into detection light and reference light.

[0015] In one embodiment, the first signal acquisition device includes a first lens and a first light detector;

[0016] The first lens is used to converge the absorbed detection light;

[0017] The first light detector is used to convert the focused detection light into an etching radio frequency signal.

[0018] In one embodiment, the reference arm includes a reference cell and a second signal acquisition device;

[0019] The reference gas in the reference cell is used to absorb the mixed light, and the absorbed mixed light is sent to the second signal acquisition device, so that the second signal acquisition device converts the absorbed mixed light into a reference radio frequency signal.

[0020] In one embodiment, the second signal acquisition device includes a second lens and a second light detector;

[0021] The second lens is used to converge the absorbed reference light;

[0022] The second light detector is used to convert the focused reference light into a reference radio frequency signal.

[0023] In one embodiment, the second signal acquisition device further includes a second reflector for reflecting the absorbed reference light to the second lens.

[0024] In one embodiment, the gas state analysis device is specifically used to:

[0025] determining an etching spectrum signal according to the etching radio frequency signal and the reference radio frequency signal;

[0026] The etching gas state is determined according to the etching spectrum signal.

[0027] In one embodiment, the gas state analysis device is specifically used to:

[0028] determining a conversion coefficient according to a reference radio frequency signal and a preset reference spectrum signal;

[0029] The etching spectrum signal is determined according to the conversion coefficient and the etching radio frequency signal.

[0030] An embodiment of the present invention further provides a gas state analysis method, comprising:

[0031] determining an etching spectrum signal according to an etching radio frequency signal from a signal acquisition device and a reference radio frequency signal from a reference arm;

[0032] The etching gas state is determined according to the etching spectrum signal.

[0033] In one embodiment, determining the etching spectrum signal according to the etching radio frequency signal from the signal acquisition device and the reference radio frequency signal from the reference arm includes:

[0034] determining a conversion coefficient according to a reference radio frequency signal and a preset reference spectrum signal;

[0035] The etching spectrum signal is determined according to the conversion coefficient and the etching radio frequency signal.

[0036] The light guiding module in the etching gas monitoring system and gas state analysis method of the embodiment of the present invention combines the signal light emitted by the signal light source light comb and the local oscillator light emitted by the local oscillator light source light comb to obtain a mixed light, and splits the mixed light into detection light and reference light. The etching gas in the plasma etching chamber absorbs the detection light, and the absorbed detection light is sent to the first signal acquisition device so that the first signal acquisition device converts the absorbed detection light into an etching radio frequency signal. The reference gas in the reference arm is used to absorb the reference light and convert the absorbed reference light into a reference radio frequency signal. The gas state analysis device determines the etching gas state according to the etching radio frequency signal and the reference radio frequency signal, which can improve the sensitivity, resolution and real-time performance of etching gas monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 is a schematic diagram of an etching gas monitoring system according to an embodiment of the present invention;

[0039] Figure 2 is a working schematic diagram of an etching gas monitoring system according to an embodiment of the present invention;

[0040] Figure 3 4 is a flow chart of a gas state analysis method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] Those skilled in the art will appreciate that the embodiments of the present invention may be implemented as a system, apparatus, device, method, or computer program product. Therefore, the present disclosure may be implemented in the following forms: entirely in hardware, entirely in software (including firmware, resident software, microcode, etc.), or in a combination of hardware and software.

[0043] In view of the problem of etching endpoint determination in the prior art, an embodiment of the present invention provides an etching gas monitoring system and a gas state analysis method, which uses two optical frequency combs with a small repetition frequency difference to convert to radio frequency detection under heterodyne interference, and combines with Fourier transform spectroscopy technology to achieve non-contact real-time detection of gas in the plasma etching chamber, including: (1) completing the locking of the repetition frequency and carrier envelope phase offset frequency of the two optical frequency combs; (2) performing gas detection in the plasma chamber; (3) performing heterodyne interference radio frequency detection through a light detector; (4) performing Fourier transform on a computer to restore spectral information; (5) determining the gas state in the plasma chamber through the spectrum. Since the signal intensity of the spectrum is proportional to the number of particles in the low energy level in the monitored plasma gas, and the number of particles in the low energy level is usually far greater than the number of particles in the high energy level, the present invention has the three characteristics of high resolution, real-time performance and high sensitivity, can simultaneously identify multiple gas components, has strong anti-interference ability, and is suitable for gas monitoring in the plasma etching process. The present invention is described in detail below with reference to the accompanying drawings.

[0044] Figure 1 Schematic diagram of an etching gas monitoring system according to an embodiment of the present invention. Figure 2 FIG. 1 is a schematic diagram of the working process of the etching gas monitoring system in an embodiment of the present invention. Figure 1-Figure 2 As shown, the etching gas monitoring system includes: a signal light source comb 111, a local oscillator light source comb 112, a light guide module 120, a plasma etching chamber 130, a first signal acquisition device 150, a reference arm 140 and a gas state analysis device.

[0045] like Figure 1 As shown, the dual-comb spectroscopy device 110 includes a signal light source comb 111 and a local oscillator light source comb 112. These can be either all-fiber lasers, all-solid-state lasers with spatial structures, or half-space, half-fiber lasers. The optical comb spectrum consists of a series of coherent lasers with equal frequency intervals and stable phase relationships. Its spectral shape resembles a comb and is referred to as an optical comb. The repetition frequency of the optical frequency comb of the present invention is above 100 MHz, but the repetition frequencies of the two combs differ slightly, typically in the Hz to kHz range, enabling delayed scanning in the time domain.

[0046] The measurement principle of a dual-comb spectrometer is similar to that of a Fourier transform spectrometer, except that it uses two optical frequency combs with slightly different repetition rates as the interferometric light source, replacing the interferometer's mechanical arm. This fully static design significantly improves the stability of the measurement system while simultaneously increasing the spectral resolution to several kHz, a four-order-of-magnitude improvement over traditional Fourier transform spectrometers. Furthermore, the sampling time can be shortened to microseconds, equivalent to real-time sampling, a six-order-of-magnitude improvement over traditional Fourier transform spectrometers.

[0047] The optical frequency combs of the present invention are all pulsed laser seed sources pumped by semiconductor lasers LD, and adopt a passive mode locking method, which is one of nonlinear polarization rotation mode locking, nonlinear amplifying ring mirror mode locking, saturable absorber mode locking, Kerr lens mode locking and carbon nanotube mode locking. Their spectra have the same central wavelength, and the operating wavelength covers the position of the gas molecule spectral absorption line that needs to be monitored.

[0048] The central wavelength depends on the gain medium in the laser resonant cavity. A suitable seed source can be selected according to the spectral position of the main components in the etching gas. Alternatively, a seed source in the near-infrared band can be directly used and then the spectrum can be broadened to cover the absorption position of the gas to be monitored in the plasma through a nonlinear optical fiber.

[0049] The light guide module 120 of the present invention is used to combine the signal light emitted by the signal light source optical comb 111 and the local oscillator light emitted by the local oscillator light source optical comb 112 to obtain mixed light, and split the mixed light into detection light and reference light.

[0050] Among them, the signal light and the local oscillator light are two beams of optical comb pulses with locked repetition frequencies but different repetition frequencies. The light guide module 120 includes a first reflector 122 and a beam splitter 121. The local oscillator light is reflected by the first reflector 122 to the beam splitter 121. The beam splitter 121 is used to combine the signal light and the local oscillator light to obtain mixed light, and then split the mixed light into detection light and reference light.

[0051] The etching gas in the plasma etching chamber 130 absorbs the probe light, causing the pulse spectrum intensity distribution of the absorbed probe light to change accordingly. The absorbed probe light is then fed into the first signal acquisition device 150, which converts it into an etching RF signal. The pulse spectrum intensity distribution of the absorbed probe light changes accordingly.

[0052] In one embodiment, the first signal acquisition device 150 includes a first lens 151 and a first light detector 152 . The first lens 151 is used to converge the absorbed detection light, and the first light detector 152 is used to convert the converged detection light into an etching radio frequency signal.

[0053] The reference gas in the reference arm 140 is used to absorb the reference light and convert the absorbed reference light into a reference radio frequency signal.

[0054] In one embodiment, the reference arm 140 includes a reference cell 141 and a second signal acquisition device.

[0055] The reference gas in the reference cell 141 is a standard sample of gas molecules, which is used to absorb the mixed light and send the absorbed mixed light to the second signal acquisition device so that the second signal acquisition device converts the absorbed mixed light into a reference radio frequency signal.

[0056] The second signal acquisition device includes a second reflector 142 , a second lens 143 and a second light detector 144 .

[0057] The second reflector 142 is used to reflect the absorbed reference light to the second lens 143 . The second lens 143 is used to converge the absorbed reference light. The second photodetector 144 is used to convert the converged reference light into a reference radio frequency signal.

[0058] The gas state analysis device is connected to the signal acquisition device 150 and the reference arm 140 respectively, and is used to determine the etching gas state according to the etching RF signal and the reference RF signal.

[0059] In specific implementation, the gas state analysis device is specifically used for:

[0060] 1. Determine the etching spectrum signal based on the etching RF signal and the reference RF signal.

[0061] In one embodiment, determining the etching spectrum signal according to the etching radio frequency signal and the reference radio frequency signal includes:

[0062] (1) Determine the conversion coefficient based on the reference radio frequency signal and the preset reference spectrum signal.

[0063] Before determining the conversion coefficient, the etching RF signal and the reference RF signal are first converted into analog to digital. The conversion coefficient m of the present application is the ratio of the preset reference spectrum signal to the reference RF signal, and the preset reference spectrum signal is the spectrum signal of the reference gas.

[0064] (2) Determine the etching spectrum signal based on the conversion coefficient and the etching RF signal.

[0065] The etching spectrum signal is the product of the conversion coefficient and the etching radio frequency signal.

[0066] In a specific implementation, the conversion coefficient is first multiplied by the etching radio frequency signal, and then the etching spectrum signal can be restored by performing Fourier transform on the product.

[0067] 2. Determine the etching gas state based on the etching spectrum signal.

[0068] The frequency and intensity attenuation information of the spectrum in the etching spectrum signal can be used to obtain the real-time change state of the gas content and composition in the plasma chamber, and determine whether the etching endpoint has been reached.

[0069] like Figure 2 As shown, the workflow of the etching gas monitoring system of this application is as follows:

[0070] 1. Lock the repetition frequency and carrier-envelope phase offset frequency of the two optical frequency combs, and the two optical frequency combs output signal light and local oscillator light respectively.

[0071] 2. After the signal light and the local oscillator light are combined, they are divided into two paths. One path is called the detection light and passes through the plasma etching chamber to be monitored. The other path is called the reference light and passes through the reference arm.

[0072] 3. Adjust the optical path and obtain heterodyne interference signals in the detectors that collect the two light paths.

[0073] The heterodyne interference signal of a dual optical frequency comb refers to the signal obtained by interfering two optical frequency combs with repetition frequencies of frep and frep+△frep respectively. The two optical frequency combs overlap in space to produce interference pulses with the repetition frequency difference △frep as the refresh frequency. The spectrum of the interference pulse corresponds one-to-one to the optical spectrum, and its conversion coefficient is m=frep / △frep.

[0074] Usually, frep is much larger than ∆frep, and the value of m can be greater than 10 6 . Since the frequency domain bandwidth of the photodetector is usually in the GHz range, it cannot directly respond to light pulses in the THz band, but the signal after the optical comb beat is in the radio frequency band, which is just within the frequency response range of the detector. Therefore, the detector filters out the high-frequency signal like a low-pass filter and only retains the beat signal in the radio frequency band. At this time, the Fourier transform spectrum of the time domain interference pattern measured by the photodetector is similar to the "radio frequency comb" structure of the optical frequency comb spectrum, and its repetition frequency is △frep, and the low-frequency "radio frequency comb teeth" and the high-frequency "optical frequency comb teeth" are one-to-one corresponding. In this way, the absorption spectrum of the sample to be tested can be converted from the spectrum to the radio frequency, realizing the down-conversion of the spectrum information. For example, for red light with a frequency of 430THz, when m is 10 6 When the frequency is converted to 430 MHz, it can be easily detected by a photodetector with a bandwidth of 1 GHz.

[0075] 4. The collected signal is transformed by fast Fourier transform to obtain the corresponding spectral information.

[0076] 5. By comparing the two signals, the real-time gas state and etching process information in the plasma etching chamber can be obtained.

[0077] In summary, the etching gas monitoring system provided by the embodiment of the present invention has the following beneficial effects:

[0078] (1) The present invention monitors the etching process in the plasma etching chamber in real time by combining dual optical frequency comb heterodyne interferometry and Fourier transform spectroscopy. Compared with other spectral detection technologies, it does not require any mechanical movement, has a faster measurement speed, and has higher spectral resolution and signal-to-noise ratio.

[0079] (2) The present invention uses dual optical frequency comb spectroscopy technology to measure the full spectrum of the optical comb, which is similar to using countless frequency and phase stable narrow linewidth lasers. The linewidth of a single comb tooth ensures the spectral resolution of natural gas detection.

[0080] (3) The measurement system of the present invention can realize a high-power optical frequency comb with an average power of tens to hundreds of watts through a single-stage or cascaded optical amplifier. The single pulse energy of each comb tooth of the optical frequency comb is relatively high, and the spectrum can be measured when the optical frequency comb seed source pulse has a low repetition frequency. At the same time, the high-power optical frequency comb is conducive to the spectrum broadening of the optical frequency comb. The output light band of the optical frequency comb can be expanded to a wider range covering ultraviolet, visible and infrared through nonlinear optical fiber, thereby realizing accurate detection of multiple gas components and broadening the application field of the present invention.

[0081] (4) The detection light can be transmitted through a long-distance optical cable to reach the area to be detected. The plasma etching chamber and the signal acquisition module can be integrated into an integrated design to achieve non-contact detection of the plasma etching area.

[0082] Based on the same inventive concept, an embodiment of the present invention also provides a gas state analysis method. Since the principle of solving the problem by this method is similar to that of the gas state analysis device in the etching gas monitoring system, the implementation of this method can refer to the implementation of the system, and the repeated parts will not be repeated.

[0083] Figure 3 FIG. 1 is a flow chart of a gas state analysis method according to an embodiment of the present invention. Figure 3 As shown, the gas state analysis method applied to the gas state analysis device as described above includes:

[0084] S101: Determine an etching spectrum signal according to an etching radio frequency signal from a signal acquisition device and a reference radio frequency signal from a reference arm.

[0085] In one embodiment, determining the etching spectrum signal based on the etching radio frequency signal from the signal acquisition device and the reference radio frequency signal from the reference arm includes:

[0086] determining a conversion coefficient according to a reference radio frequency signal and a preset reference spectrum signal;

[0087] The etching spectrum signal is determined according to the conversion coefficient and the etching radio frequency signal.

[0088] S102: Determine the etching gas state according to the etching spectrum signal.

[0089] Figure 3 The execution subject of the gas state analysis method shown in the figure can be a gas state analysis device. Figure 3 As can be seen from the process shown, the gas state analysis method of the embodiment of the present invention first determines the etching spectrum signal based on the etching RF signal from the signal acquisition device and the reference RF signal from the reference arm, and then determines the etching gas state based on the etching spectrum signal, which can improve the sensitivity, resolution and real-time performance of etching gas monitoring.

[0090] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0091] Those skilled in the art will also appreciate that the various illustrative logical blocks, units, and steps listed in the embodiments of the present invention can be implemented by electronic hardware, computer software, or a combination of the two. To clearly demonstrate the interchangeability of hardware and software, the various illustrative components, units, and steps described above have generally described their functions. Whether such functions are implemented by hardware or software depends on the specific application and the design requirements of the entire system. Those skilled in the art may use various methods to implement the described functions for each specific application, but such implementation should not be understood as exceeding the scope of protection of the embodiments of the present invention.

[0092] The various illustrative logic blocks, units, or devices described in the embodiments of the present invention can be implemented or operated by a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field programmable gate array or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. The general-purpose processor can be a microprocessor, and optionally, the general-purpose processor can also be any conventional processor, controller, microcontroller, or state machine. The processor can also be implemented by a combination of computing devices, such as a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a digital signal processor core, or any other similar configuration.

[0093] The steps of the methods or algorithms described in the embodiments of the present invention may be directly embedded in hardware, a software module executed by a processor, or a combination of the two. The software module may be stored in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. For example, the storage medium may be connected to the processor so that the processor can read information from the storage medium and write information to the storage medium. Alternatively, the storage medium may also be integrated into the processor. The processor and storage medium may be provided in an ASIC, which may be provided in a user terminal. Alternatively, the processor and storage medium may also be provided in different components in the user terminal.

[0094] In one or more exemplary designs, the above-mentioned functions described in the embodiments of the present invention can be implemented in hardware, software, firmware, or any combination of the three. If implemented in software, these functions can be stored on a computer-readable medium or transmitted in the form of one or more instructions or codes on a computer-readable medium. Computer-readable media include computer storage media and communication media that facilitate the transfer of computer programs from one location to another. Storage media can be any available medium that can be accessed by a general or special computer. For example, such computer-readable media can include but are not limited to RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store program code in the form of instructions or data structures and other forms that can be read by a general or special computer, or a general or special processor. In addition, any connection can be appropriately defined as a computer-readable medium. For example, if the software is transmitted from a website, server or other remote resource via a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless methods such as infrared, wireless, and microwave, it is also included in the definition of computer-readable media. The disks and discs mentioned above include compact disks, laser disks, optical disks, DVDs, floppy disks, and Blu-ray discs. Disks typically reproduce data magnetically, while discs typically reproduce data optically with lasers. Combinations of the above may also be included in computer-readable media.

Claims

1. An etching gas monitoring system, characterized in that: include: A signal light source comb, a local oscillator light source comb, a light guide module, a plasma etching chamber, a first signal acquisition device, a reference arm, and a gas state analysis device; the spectra of the signal light source comb and the local oscillator light source comb have the same central wavelength, and the operating wavelength covers the position of the gas molecule spectral absorption line to be monitored; The light guide module is used to combine the signal light emitted by the signal light source optical comb and the local oscillator light emitted by the local oscillator light source optical comb to obtain mixed light, and split the mixed light into detection light and reference light; The etching gas in the plasma etching chamber is used to absorb the detection light, and the absorbed detection light is sent to the first signal acquisition device, so that the first signal acquisition device converts the absorbed detection light into an etching radio frequency signal; The reference gas in the reference arm is used to absorb the reference light and convert the absorbed reference light into a reference radio frequency signal; The gas state analysis device is connected to the signal acquisition device and the reference arm respectively, and is used to determine the etching gas state according to the etching RF signal and the reference RF signal; Wherein, the gas state analysis device is specifically used for: determining an etching spectrum signal according to the etching radio frequency signal and the reference radio frequency signal; determining the etching gas state according to the etching spectrum signal; Wherein, the gas state analysis device is further used for: Determining a conversion coefficient based on the reference radio frequency signal and a preset reference spectrum signal; The etching spectrum signal is determined according to the conversion coefficient and the etching radio frequency signal.

2. The etching gas monitoring system according to claim 1, characterized in that: The light guide module includes a first reflector and a beam splitter; The local oscillator light is reflected by the first reflector to the beam splitter; The beam splitter is used to combine the signal light and the local oscillator light to obtain mixed light, and to separate the mixed light into detection light and reference light.

3. The etching gas monitoring system according to claim 1, characterized in that: The first signal acquisition device includes a first lens and a first light detector; The first lens is used to converge the absorbed detection light; The first light detector is used to convert the focused detection light into the etching radio frequency signal.

4. The etching gas monitoring system according to claim 1, characterized in that: The reference arm includes a reference cell and a second signal acquisition device; The reference gas in the reference cell is used to absorb the mixed light, and the absorbed mixed light is sent to the second signal acquisition device, so that the second signal acquisition device converts the absorbed mixed light into a reference radio frequency signal.

5. The etching gas monitoring system according to claim 4, characterized in that: The second signal acquisition device includes a second lens and a second light detector; The second lens is used to converge the absorbed reference light; The second light detector is used to convert the focused reference light into the reference radio frequency signal.

6. The etching gas monitoring system according to claim 5, characterized in that: The second signal acquisition device further includes a second reflector, configured to reflect the absorbed reference light to the second lens.

7. A gas state analysis method using the etching gas monitoring system according to any one of claims 1 to 6, characterized in that: include: determining an etching spectrum signal according to an etching radio frequency signal from a signal acquisition device and a reference radio frequency signal from a reference arm; determining the state of the etching gas according to the etching spectrum signal; Wherein, determining the etching spectrum signal according to the etching radio frequency signal from the signal acquisition device and the reference radio frequency signal from the reference arm includes: Determining a conversion coefficient based on the reference radio frequency signal and a preset reference spectrum signal; The etching spectrum signal is determined according to the conversion coefficient and the etching radio frequency signal.

Images