JP4041212B2 - Semiconductor device manufacturing method and plasma processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention aims to improve the yield of objects to be processed such as semiconductor substrates by measuring in-situ submicron foreign matters suspended in the plasma processing chamber during processing without being affected by disturbances such as plasma emission. The present invention relates to a semiconductor manufacturing method, a plasma processing method and an apparatus therefor.
[0002]
[Prior art]
As conventional techniques for monitoring foreign matters floating in the plasma processing chamber, Japanese Patent Laid-Open No. 57-118630 (Prior Art 1), Japanese Patent Laid-Open No. 3-25355 (Prior Art 2), Japanese Patent Laid-Open No. 3-147317 ( Japanese Patent Laid-Open No. 6-82358 (prior art 4) and Japanese Patent Laid-Open No. 6-124902 (prior art 5).
[0003]
In the prior art 1, the means for irradiating the reaction space with parallel light having a spectrum different from the spectrum of the self-emitting light in the reaction space, and the scattering from the fine particles generated in the reaction space upon receiving the parallel light irradiation. A vapor deposition apparatus having a means for detecting light is known.
Further, in the prior art 2, in a fine particle measuring apparatus for measuring fine particles adhering to the surface of a semiconductor device substrate and floating fine particles using scattering by laser light, the wavelength is the same and the mutual phase difference is present. A laser beam phase modulation unit that generates two laser beams modulated at a predetermined frequency, an optical system that intersects the two laser beams in a space containing the fine particles to be measured, and the 2 A light detection unit that receives light scattered by fine particles to be measured in a crossed region of the laser beams and converts it into an electrical signal, and the laser light phase modulation unit in the electrical signal by the scattered light And a signal processing unit for extracting a signal component having the same or twice the frequency as that of the phase modulation signal and a phase difference with the phase modulation signal is known. There.
[0004]
The prior art 3 includes a step of generating in-situ light scattered in the reaction vessel by scanning irradiation with coherent light, and a step of detecting the light scattered in the reactor. A technique for measuring contamination in the reactor by analyzing scattered light is described.
The prior art 4 includes laser means for generating laser light, scanner means for scanning a region in a reaction chamber of a plasma processing tool containing particles to be detected with the laser light, and particles in the area. A particle detector is described having video camera means for generating a video signal of scattered laser light and means for processing and displaying an image of said video signal.
The prior art 5 includes a camera device for observing a plasma generation region in the plasma processing chamber, a data processing unit for processing images obtained by the camera device to obtain target information, and the data processing unit. A plasma processing apparatus comprising: a control unit that controls at least one of exhaust means, process gas introduction means, high-frequency voltage application means, and purge gas introduction means so as to reduce particles based on information obtained by Has been.
[0005]
Japanese Patent Laid-Open No. 63-71633 (Prior Art 6) is known as a prior art relating to a fine particle measuring apparatus used for high cleaning process management such as semiconductor and chemical manufacturing processes. This prior art 6 includes means for modulating the intensity of a laser beam at a constant frequency in a particle detector that irradiates a minute region of a container through which a sample specimen flows and detects scattered light from particles in the sample. There is described a particulate counter comprising a phase detector for measuring a signal from a detector having the same frequency as the intensity modulation frequency of the laser beam.
[0006]
[Problems to be solved by the invention]
In the plasma processing apparatus, a reaction product generated by the plasma processing is deposited on the wall surface or electrode of the plasma processing chamber and peels off as time passes to become floating foreign matters. This floating foreign substance adheres to the object to be processed during plasma processing and causes defects, or is trapped at the plasma bulk-sheath interface, and the plasma processing is terminated and the plasma discharge is stopped at the moment the plasma processing is stopped. Fall on the surface and cause poor properties and poor appearance as adhered foreign matter. Eventually, the yield of objects to be processed such as semiconductor substrates was reduced.
On the other hand, high integration of circuit patterns formed on an object to be processed such as a semiconductor substrate (for example, in the semiconductor field, 256 Mbit DRAMs and further 1 Gbit DRAMs have advanced to high integration, and the minimum line width of circuit patterns is 0.25. With the progress of miniaturization to ˜0.18 μm), it has become necessary to measure even minute sub-micron foreign matter floating in or near the plasma during plasma processing.
[0007]
Therefore, in a plasma processing apparatus, it is required to measure even a sub-micron foreign matter floating in or near the plasma during plasma processing without being affected by disturbance such as plasma emission. However, since the plasma emission has a continuous wavelength spectrum from the ultraviolet region to the near-infrared region, the submicron minute foreign matter floating in the plasma or in the vicinity thereof is caused by the spectrum described in the prior art 1. It is difficult to detect separately from plasma emission.
Further, in the detection of minute foreign matter by laser illumination / scattered light detection, there is a large background noise such as scattered light on the inner wall of the processing chamber in addition to plasma emission. This background noise is a factor that determines the detection limit because the detector output is saturated by the background noise when trying to increase the foreign matter signal, for example, by improving the detector sensitivity or increasing the laser output. It was.
[0008]
As described above, in any of the related arts 1 to 5, it is intended to detect very weak scattered light obtained from submicron minute foreign matters floating in or near the plasma separately from plasma emission. The point was not considered.
Further, it has not been considered that weak scattered light is to be detected from large background noise such as inner wall scattered light having the same wavelength as that of foreign matter scattered light.
In the prior art 6, particles in a sample flowing in a container are measured. Naturally, very weak scattered light obtained from submicron minute foreign matters floating in or near the plasma is separated from plasma emission. Thus, the point to be detected is not taken into consideration.
[0009]
The object of the present invention is to greatly improve the detection sensitivity of the plasma processing chamber to detect small foreign particles suspended up to submicron in the plasma processing chamber separately from the plasma emission during the plasma processing in order to solve the above problems. Thus, it is an object of the present invention to provide a plasma processing method and apparatus for improving the yield by enabling real-time monitoring of the contamination state in the plasma processing chamber.
Another object of the present invention is to selectively separate scattered light caused by minute foreign particles suspended up to submicron in or near the plasma in the plasma processing chamber from plasma emission and selectively remove large background noise. An object of the present invention is to provide a method for manufacturing a semiconductor capable of manufacturing a high-quality semiconductor with a high yield by enabling detection to greatly improve detection sensitivity and enable real-time monitoring of a contamination state in a plasma processing chamber. .
[0011]
[Means for Solving the Problems]
To achieve the above objective, In the present invention, a semiconductor is generated by generating plasma in a processing chamber and processing a semiconductor substrate by the plasma. device Manufacturing semiconductor device Having different wavelengths from each other, Specificity different from the excitation frequency of the plasma and its integer multiple or the emission frequency of the plasma and its integral multiple An irradiation optical system that irradiates the processing chamber with a plurality of beams that have been intensity-modulated at a predetermined frequency, and a plurality of beams irradiated by the irradiation optical system separates scattered light obtained from the processing chamber by the different wavelength components. Scattered light detection optical system that receives light and converts it into a plurality of signals, and the intensity modulation from a plurality of signals obtained from the scattered light detection optical system specific Using a plasma floating particle measuring apparatus comprising a foreign material signal extracting means for separating and detecting a plurality of signals indicating foreign particles floating in or near the plasma by extracting frequency components of the plasma It is characterized in that foreign matter floating in or near the plasma generated in the processing chamber is measured.
Further, the present invention provides a semiconductor in which a plasma is generated in a processing chamber and a semiconductor substrate is processed by the plasma. device Manufacturing semiconductor device In the manufacturing method of specific Having a wavelength of Different from the excitation frequency of the plasma and its integral multiple or the emission frequency of the plasma and its integral multiple; An irradiation optical system that irradiates the processing chamber with a plurality of beams that are intensity-modulated at different frequencies, and a scattered light that is obtained from the processing chamber by the plurality of beams irradiated by the irradiation optical system. specific Scattered light detection optical system that receives light separated into wavelength components and converts it into a signal, and in the vicinity of plasma by extracting different frequency components that have been intensity-modulated from signals obtained from the scattered light detection optical system The plasma floating foreign matter measuring device provided with a foreign matter signal extracting means for detecting and detecting a plurality of signals indicating foreign matters floating on the plasma separately from those caused by the plasma and floating in or near the plasma generated in the processing chamber It is characterized by measuring foreign matter.
[0013]
Also, The present invention provides a plasma processing method for generating plasma in a processing chamber and processing an object to be processed with the plasma, having different wavelengths, Specificity different from the excitation frequency of the plasma and its integer multiple or the emission frequency of the plasma and its integral multiple An irradiation optical system that irradiates the processing chamber with a plurality of beams that have been intensity-modulated at a predetermined frequency, and a plurality of beams irradiated by the irradiation optical system separates scattered light obtained from the processing chamber by the different wavelength components. Scattered light detection optical system that receives light and converts it into a plurality of signals, and the intensity modulation from a plurality of signals obtained from the scattered light detection optical system specific And a foreign substance signal extraction means for detecting a signal indicating a foreign substance suspended in or near the plasma by separating the frequency component of the plasma from the plasma and using the plasma floating foreign substance measuring device. It measures the foreign matter floating in the plasma generated in the vicinity or in the vicinity thereof.
[0014]
Further, the present invention provides a plasma processing method for generating plasma in a processing chamber and processing an object to be processed with the plasma. specific Having a wavelength of Different from the excitation frequency of the plasma and its integral multiple or the emission frequency of the plasma and its integral multiple; An irradiation optical system that irradiates the processing chamber with a plurality of beams that are intensity-modulated at different frequencies, and a scattered light that is obtained from the processing chamber by the plurality of beams irradiated by the irradiation optical system. specific Scattered light detection optical system that receives light separated into wavelength components and converts it into a signal, and in the vicinity of plasma by extracting different frequency components that have been intensity-modulated from signals obtained from the scattered light detection optical system The plasma floating foreign matter measuring device provided with a foreign matter signal extracting means for detecting and detecting a plurality of signals indicating foreign matters floating on the plasma separately from those caused by the plasma and floating in or near the plasma generated in the processing chamber It is characterized by measuring foreign matter.
Also, The present invention provides the above The semiconductor device manufacturing method and the plasma processing method are used as described above. Plasma floating particle measuring device Said Noise removing means for removing noise components from a plurality of signals indicating floating foreign substances detected from the foreign substance signal extracting means. More It is characterized by having.
[0017]
Further, the present invention provides the above In the manufacturing method of a semiconductor device and the plasma processing method, the plasma floating particle measuring apparatus used is the above-mentioned. Irradiation optics Is Scanning means for scanning the beam on the object to be processed; More It is characterized by having.
Further, the present invention provides the above In the manufacturing method of a semiconductor device and the plasma processing method, the plasma floating particle measuring apparatus used is the above-mentioned. The scattered light detection optical system receives backscattered light obtained from the processing chamber. To do It is characterized by.
Further, the present invention provides the above In the manufacturing method of a semiconductor device and the plasma processing method, the plasma floating particle measuring apparatus used is the above-mentioned. Scattered light detection optical system Of the scattered light obtained from the processing chamber, A polarized light component different from the polarized beam irradiated by the irradiation optical system is received.
Further, the present invention provides the above In the manufacturing method of a semiconductor device and the plasma processing method, the plasma floating particle measuring apparatus used is the above-mentioned. Irradiation optics Is The optical axes of a plurality of beams are formed by adjacent parallel axes.
Further, the present invention provides the above In the manufacturing method of a semiconductor device and the plasma processing method, the plasma floating particle measuring apparatus used is the above-mentioned. Irradiation optics Is A plurality of beams have the same optical axis.
As described above, according to the above configuration, the minute foreign matter floating in or near the plasma is removed from the plasma emission to the wavelength / frequency region. By In the case of detecting separately, by obtaining a plurality of detection signals indicating minute foreign matters, large background noise such as inner wall scattered light is removed, and only the signal due to foreign matter scattered light is selectively improved and S / N is observed. As a result, it is possible to detect a sub-micron foreign substance floating in or near the plasma.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Semiconductor manufacturing method for manufacturing high-quality semiconductor elements and the like by enabling real-time monitoring of the contamination state in the processing chamber according to the present invention and reducing defective substrates (objects to be processed) due to adhesion of foreign matters Embodiments of the apparatus will be described with reference to the drawings.
As a processing apparatus for manufacturing a semiconductor element or the like, there are a plasma etching apparatus, a plasma film forming apparatus, and the like. These processing apparatuses generate plasma in a processing chamber and perform etching on a substrate to be processed, or perform film formation by CVD or sputtering.
[0019]
Hereinafter, an embodiment for performing real-time monitoring of a contamination state (occurrence state of a foreign substance or the like) in a processing chamber in these processing apparatuses will be described with reference to FIGS.
First, a plasma processing apparatus according to the present invention will be described with reference to FIG. As shown in FIG. 1, the plasma processing apparatus 201 generates a plasma 208 on an electrode 203 on which a substrate to be processed (object to be processed) 4 is placed, and the generated plasma 208 is applied to the substrate 4 to be processed. To process. In this plasma processing apparatus 201, the reaction product is not exhausted and part of the reaction product is deposited on the wall surface and the electrode in the processing chamber 1 with the time during which plasma processing is performed on the substrate 4 to be processed. Further, as the substrate to be processed 4 is subjected to plasma processing on a large number of substrates, a lot of deposited reaction products are peeled off and float in a large amount in the processing chamber 1 and then enter the plasma 208. Most of the floating foreign substances are negatively charged and are confined in the plasma, but when the processing is finished, the output of the power amplifier 206 is stopped and at the same time, the foreign substances adhere to the surface of the substrate 4 to be processed. Thus, a defective substrate 4 to be treated is produced.
In particular, with the progress of high integration of circuit patterns formed on the substrate 4 to be processed, in the field of semiconductors, the minimum line width of circuit patterns is 0.25 to 0.18 μm, and the miniaturization continues. Therefore, even if the size of the foreign matter adhering to the surface of the substrate to be processed 4 is on the order of submicron, a defective substrate 4 to be processed is produced.
[0020]
Next, a parallel plate plasma etching apparatus which is one of plasma etching apparatuses as the plasma processing apparatus 201 will be described with reference to FIG. An upper electrode 202 and a lower electrode 203 which are parallel to each other by forming a gap for forming the plasma 208 are arranged in the plasma processing chamber 1. On the lower electrode 203, the substrate 4 to be processed is installed. Incidentally, an etching gas is supplied from the outside between the upper electrode 202 and the lower electrode 203 in the processing chamber. The output voltage of the power amplifier 206 is modulated by the high frequency signal from the signal generator 205. The modulated high frequency voltage of about 380 to 800 kHz is distributed by the distributor 207 and applied between the upper electrode 202 and the lower electrode 203. Therefore, by discharge between both electrodes, the supplied etching gas is turned into plasma to generate plasma 208, and the substrate 4 to be processed is etched with the active species. Further, the etching processing apparatus monitors the progress of etching and detects the end point as accurately as possible to perform the etching process so as to obtain a predetermined pattern shape and depth. That is, when the end point is detected, the output of the power amplifier 206 is stopped, and then the substrate 4 to be processed is unloaded from the processing chamber 1.
In addition, there is a plasma etching apparatus that introduces a resonated microwave and turns it into a plasma by a magnetic field or an electric field for etching.
As a plasma film forming apparatus, for example, a CVD gas is supplied from an upper electrode, and the supplied CVD gas is converted into plasma by a high frequency power and reacted to form a film on a substrate to be processed.
[0021]
Next, the basic principle of the plasma floating particle measuring apparatus 100 according to the present invention will be described with reference to FIGS. The plasma floating particle measuring apparatus 100 needs to measure a particle floating in or near the plasma 208 generated in the plasma processing apparatus. FIG. 2 shows an observation example of plasma emission waveform with respect to time during etching (relationship between time and emission intensity [V]) when the plasma excitation frequency is 400 kHz. As shown in FIG. 2, it can be seen that the plasma emission intensity [V] periodically changes in synchronization with the plasma excitation frequency of 400 kHz. FIG. 3 shows an example (relationship between frequency [MHz] and emission intensity [mV]) obtained by observing the emission waveform with a spectrum analyzer. As shown in FIG. 3, harmonic components having a fundamental frequency of 400 kHz and integer multiples of 800 kHz, 1200 kHz, 1600 kHz, and so on are observed. In addition, as shown in FIG. 3, the emission intensity is about 1.9 mV for a fundamental frequency of 400 kHz and twice that for a noise component having various frequency components of about 0.7 mV, about 3 times that of 800 kHz. About 1200 mV is observed at 1200 kHz, and about 1.4 mV is observed at 4 times 1600 kHz. FIG. 4 shows the frequency spectrum of the plasma emission with the noise component shown in FIG. 3 removed, and detection from floating foreign substances in the plasma when the laser beam having a wavelength of 633 nm (red) is irradiated with intensity modulation at a frequency of 300 kHz. 2 shows a frequency spectrum of emitted scattered light. That is, as shown in FIG. 4, when the plasma excitation frequency is 400 kHz, the frequency spectrum of plasma emission is discretely expressed as a DC component 240 and a 400 kHz component 241 on top of noise components having various frequency components. It can be seen that there is a free area in the frequency domain. As is clear from FIG. 4, light having various wavelength components (mainly about 300 nm (near ultraviolet light) to 490 nm (blue)) is emitted from the plasma 208 generated on the substrate 4 to be processed. The floating sub-micron foreign matter is irradiated.
[0022]
Therefore, for example, laser light having a wavelength of 633 nm (red) is intensity-modulated at a frequency of, for example, 300 kHz, which is different from the frequency of the plasma emission, and the intensity-modulated laser light is incident into the processing chamber 1 to be included in the detection light. If only the wavelength 633 nm and the frequency 300 kHz component, that is, the peak (in the case of laser beam wavelength separation + modulation / synchronous detection) 242 is taken out, scattered light from foreign matter on the order of submicron will be converted into various frequency components and various wavelengths. It becomes possible to detect separately from the plasma emission having a noise component composed of the components. In this way, by extracting from both the wavelength component of the laser beam emitted from the detection light and the frequency component (modulation / synchronous detection) whose intensity is modulated, scattered light from foreign matter on the order of submicron can be detected at various frequencies. It becomes possible to detect separately from plasma emission having noise components composed of components and various wavelength components. If modulation / synchronous detection is not performed only by wavelength separation of the laser beam, the scattered light from the foreign matter is buried in a direct current component due to plasma emission, and the foreign matter cannot be detected. By the way, the wavelength of the laser light to be irradiated may be red and infrared light having a long wavelength different from about 300 nm (near ultraviolet light) to 490 nm (blue) where the plasma mainly emits light. In order to obtain a large amount of scattered light from foreign matters on the order of microns, it is preferable to use a wavelength shorter than green (for example, purple or ultraviolet light). In this way, even if laser light having a wavelength component emitted from plasma is irradiated, extraction from both the wavelength component of the irradiated laser beam and the intensity-modulated frequency component from the detection light enables submicron order. Scattered light from the foreign matter can be detected separately from plasma emission having noise components.
[0023]
Next, a first embodiment of the foreign matter measuring apparatus 100 floating in or near the plasma according to the present invention will be described. 1 and 5 show a first embodiment of a plasma floating particle measuring apparatus 100. FIG. The plasma floating particle measuring apparatus 100 includes a laser irradiation optical system 101, a scattered light detection optical system 102, and a signal processing / control system 103.
First, the laser irradiation optical system 101 emits a solid laser beam having a wavelength of 532 nm (excited by a semiconductor laser), a He—Ne laser beam having a wavelength of 633 nm, an Ar laser beam having a wavelength of 514.5 nm, a semiconductor laser beam having a wavelength of 780 nm, and the like. A P-polarized beam 9 emitted from the laser light source 8 is incident on the multichannel intensity modulator 10. As the multi-channel intensity modulator 10, a multi-channel AO (Acousto-Optical) modulator or a disk in which a P-polarized beam is separated into a plurality of light by a separation optical system and an opening is formed for each separated light beam. A plurality of mechanical intensity modulators configured to rotate at high speed can be used. For example, an AO modulator as the multi-channel intensity modulator 10 is different from the frequency of plasma emission output from each of the oscillators 13 and 14 based on the control signal 120 from the computer 55, for example, frequencies 300 kHz, 500 kHz, duty 40 Since a rectangular wave signal of ˜60% (preferably 50% duty) is applied, the incident P-polarized beam 9 is intensity-modulated at these frequencies. The two beams 601 and 602 that are modulated in parallel with each other are expanded by the beam expander 150, and the two expanded beams are extremely deep by the optical system 160 (300 mm larger than the diameter of the substrate 4 to be processed). Are converted into two focused beams. That is, by inputting signals having different frequencies from the oscillators (signal generators) 13 and 14 to the respective channels of the two-channel intensity modulator 10, each of the two-channel intensity modulators 10 is modulated at a different frequency. Two outgoing beams 601 and 602 are obtained. However, the different modulation frequencies modulated by each of the two-channel intensity modulators 10 are 400 kHz and its harmonic components (double 800 kHz, triple 1200 kHz, etc.) when the plasma excitation frequency is 400 kHz. It is necessary to avoid the frequency (for example, 300 kHz, 500 kHz, etc.).
[0024]
Two parallel beams 601 and 602 whose optical axes are adjusted and close to each other are P-polarized light, are reflected by a galvano mirror (optical scanning means) 18 that passes through the polarization beam splitter 17 and is driven at high speed, and are made of a quartz window. The light passes through the window 7 and enters the plasma processing chamber 1 to scan the entire surface of the substrate 4 to be processed. As described above, by using the two beams 601 and 602 having a very deep focal depth of 300 mm or more and a diameter of about 10 μm to 30 μm, it is possible to scan the entire surface of the substrate 4 to be processed with a uniform energy density. It becomes. Further, in the plasma processing apparatus, it is considered that a large amount of foreign matter exists near the plasma sheath boundary surface. Therefore, the two beams 601 and 602 are irradiated so as to pass near the plasma sheath boundary surface immediately above the substrate 4 to be processed. Is desired. Therefore, it is necessary to be able to adjust the irradiation position in the height direction of the two beams 601 and 602 with respect to the plasma processing chamber 1. That is, it is necessary to optimize the irradiation position in the height direction of the two beams 601 and 602.
[0025]
Furthermore, when the two beams 601 and 602 scanned with the uniform energy density are irradiated to the floating foreign matter 209 in or near the plasma 208, the floating foreign matter 209 is scattered. The scattered light backscattered to the same optical axis as the incident beams 601 and 602 in the foreign matter scattered light 210P is reflected by the galvanometer mirror (optical scanning means) 18, and the S polarization component 210 is reflected by the polarization beam splitter 17. The light is condensed on the incident end face 20 of the optical fiber 30 made of quartz or the like by the imaging lens 19 made of quartz or the like. Since the directly reflected light from the wall surface 1W of the processing chamber 1 and the observation window 7 has the same P-polarized light as the incident light 601 and 602, it passes through the polarization beam splitter 17 and does not enter the optical fiber 30. As described above, most of the directly reflected light from the wall surface 1W of the processing chamber 1 and the observation window 7 can be optically erased.
In the above description, the case of P-polarization illumination and S-polarization detection has been described. However, the present invention is not limited to this, and S-polarization illumination and P-polarization detection may be used. In this case, it is necessary to reverse the relationship between reflection and transmission in the polarization beam splitter 17.
[0026]
As shown in FIG. 6, the center 60 of the substrate to be processed 4 and the incident end face 20 of the optical fiber 30 are in an imaging relationship, but the fiber bundle area (light receiving area) 70 of the incident end face 20 is defocused. The scattered light from both ends 61 and 62 of the substrate 4 to be processed is of a size that can be detected (area 65 shown in FIG. 7). Therefore, in combination with the two beams 601 and 602, uniform energy illumination and uniform sensitivity detection can be performed with respect to minute floating foreign matters over the entire surface of the substrate 4 to be processed.
The output end of the optical fiber 30 is connected to the monochromator 40, and the same wavelength component (532 nm, 633 nm, 514.5 nm, or 780 nm) as the laser light 9 is extracted, and a photoelectron image multiplier, an avalanche photodiode, etc. The photoelectric conversion element 42 performs photoelectric conversion. As a spectroscope, it is also possible to perform wavelength separation using an interference filter instead of a monochromator. In the signal processing / control system 103, the detection signal is amplified by a current-voltage conversion amplifier 44 having a bandwidth of about 500 kHz that is sufficiently wider than the laser modulation frequency, and then sent to a synchronous detection circuit 46, 47 such as a lock-in amplifier. It is done. In each of the synchronous detection circuits 46 and 47, the intensity modulation frequency (for example, 300 kHz, 500 kHz) output from each of the oscillators 13 and 14 used for modulation of the laser light, a desired duty (for example, 40 to 60%, preferably 50%) rectangular wave signals 131 and 141 are used as reference signals, and by synchronous detection, a foreign matter scattered light component having an intensity modulation frequency (for example, 300 kHz, 500 kHz) is extracted from the detection signal, and the modulation frequency (for example, 300 kHz, 500 kHz) component Other frequency components are removed. As a result, the outputs of the synchronous detection circuits 46 and 47 are signals separated from the plasma emission in both the wavelength region and the frequency region, as shown in FIG.
[0027]
Next, a signal observed when a foreign substance exists in the plasma processing chamber 1 will be described with reference to FIG. FIG. 8 shows the time change of the output at a certain scanning position on the substrate to be processed among the outputs of the synchronous detection circuits 46 and 47 obtained while scanning the two laser beams 601 and 602. Of the signals 501 and 502, the peak signals 501a to 501e and the peak signals 502a to 502e are foreign matter scattering signals. The foreign matter scattering signals 501a and 502a, 501b and 502b,..., 501e and 502e are detected at times shifted by a time interval Δt determined by the interval between the beams 601 and 602 and the scanning speed, respectively. At this time, the output I is due to noise that cannot be removed by the polarization separation described above, among the background noise generated from the inner wall of the processing chamber 1, the observation window 7, and the like. Since the DC level due to the background noise is considered to be the same level for both the signals 501 and 502, the DC noise due to the background scattered light is obtained by subtracting the signal 501 from the signal 502 in the signal processing circuit 52 such as a subtraction amplification circuit. The components are eliminated, and further amplification processing is performed to obtain two signals 503 appearing positively and negatively with respect to the same floating minute foreign substance as shown in FIG. Since the obtained signal 503 observes a scattered signal due to the same floating minute foreign matter in a short time, it observes a time derivative of the foreign matter scattered signal intensity. Therefore, when the signal 503 is integrated by the signal processing circuit 53 such as an integration circuit, as shown in FIG. 8D, the foreign substance signal 504 indicating one large time width indicated by the above time interval for each floating minute foreign substance. Is obtained.
[0028]
The computer 55 sends a scanning control signal to the galvanometer mirror (optical scanning means) 18 through the driver 56, and sequentially detects the foreign matter signal 504 indicating a large time width at each scanning position while scanning the two beams 601 and 602. It can be stored in an internal memory (not shown) or a storage device 57 provided outside in units of the substrate 4 to be processed. When the plasma processing (for example, etching, CVD, etc.) is completed on the substrate 4 to be processed, the substrate 4 to be processed is unloaded from the processing chamber 1 and floating fine foreign matter on the order of submicron with respect to one substrate 4 to be processed. Measurement ends.
The computer 55 can output the detection signal of the floating minute foreign matter at each scanning position stored in the storage device 57 for each substrate to be processed to an output means such as a display 58.
[0029]
If the computer 55 wants to determine the number of fine foreign substances 209 floating in the plasma or the vicinity thereof in units of the substrate 4 to be processed, every time the foreign substance signal 504 scans the galvanometer mirror 18 once. It can be obtained by counting. When it is desired to obtain the number of fine foreign substances 209 floating in the vicinity of the plasma in the unit of the substrate 4 to be processed, the galvano mirror 18 is rotated at a predetermined time interval to thereby provide two beams 601 and 602. May be scanned multiple times.
In this way, since the computer 55 can grasp the state of occurrence of the floating fine foreign matter, the number of the measured floating fine foreign matters increases as the cumulative discharge time corresponding to the number of processed substrates 4 increases. As a result, the cause can be estimated and countermeasures can be taken so that floating fine foreign matter does not occur, and the cleaning time of the processing chamber 1 can be accurately determined.
[0030]
Further, by scanning the two beams 601 and 602 together with the galvanometer mirror 18, two detection signals 501 and 502 are obtained from the same floating minute foreign matter. Therefore, in the signal processing circuit 52, a signal indicating the floating minute foreign matter. Can be emphasized to obtain a floating minute foreign matter signal having a high S / N ratio. For example, the two detection signals 501 and 502 are temporarily stored in the image memory in the signal processing circuit 52 and are read out in a state where there is no time lag as shown in FIGS. 9A and 9B. Two detection signals 501 ′ and 502 ′ having no noise are obtained, and the obtained signal 503 ′ is emphasized by inverting one of the obtained signals and taking the difference between the two signals, as shown in FIG. You can also get
In this way, since the computer 55 can grasp the state of occurrence of the floating fine foreign matter, the number of the measured floating fine foreign matters increases as the cumulative discharge time corresponding to the number of processed substrates 4 increases. As a result, the cause can be estimated and countermeasures can be taken so that floating fine foreign matter does not occur, and the cleaning time of the processing chamber 1 can be accurately determined.
As described above, according to the first embodiment, by using two beams, weak foreign matter scattered light is detected separately from plasma emission in two regions of wavelength and frequency, and the above subtraction and integration processes are performed. Eliminates large background noise such as scattered light from the inner wall and integrates (temporal enlargement processing) to selectively detect only the signal due to scattered light, improving the sensitivity to detecting foreign objects. Thus, it is possible to detect a sub-micron-order minute foreign substance floating in or near the plasma, which is expected to be difficult to detect.
[0031]
In the first embodiment, two beams are used. However, it is possible to use three or more beams. In that case, if signal processing similar to that in the first embodiment is performed using scattered signals from adjacent beams, the scanning range of each beam can be narrowed. It is also possible to shorten the inspection time. Further, if the number of beams is increased, the entire wafer surface can be detected almost simultaneously.
Further, since the scattered light detection optical system 102 is configured to detect the backscattered light, it becomes possible to easily detect foreign substances floating in or near the plasma in synchronization with the scanning of the galvanometer mirror 18. The irradiation optical system 101 and the scattered light detection optical system 102 can be simplified (compact).
With these effects, it becomes possible to monitor the contamination status in the plasma processing chamber in real time, and the effect of reducing the occurrence of defective substrates to be processed due to foreign matter adhesion and the time for cleaning the apparatus can be accurately grasped. An effect is born. In addition, since the frequency of the foreign matter advance check work using the dummy wafer can be reduced, the effects of cost reduction and productivity improvement are produced.
[0032]
Further, it is necessary to devise so that a reaction product or the like by the plasma treatment does not adhere and accumulate on the inner surface of the observation window 7. For example, it is possible to prevent the reaction product from adhering to the inner surface of the observation window 7 by providing a rectangular tube-shaped shield 70 that protrudes so that the reaction product does not enter as much as possible. In the y-axis direction, it is necessary to narrow the distance between the shields 70 facing each other, and in the x-axis direction, the distance between the shields 59 facing each other must be widened so that it can be scanned by the galvanometer mirror 18 and widened toward the inside. There is. In addition, by providing an exhaust port for exhausting reaction products and the like in the vicinity of the outside of the shield 59, the reaction products and the like are prevented from adhering to the inner surface of the observation window 7 through which two beams 601 and 602 are incident. can do. In addition, an observation that two beams 601 and 602 are further incident by flowing a gas (for example, an inert gas or a processing gas) that does not affect the plasma processing from one shield 59 to the other shield 59. It is possible to prevent reaction products and the like from adhering to the inner surface of the window 7.
[0033]
Next, a second embodiment of the plasma floating particle measuring apparatus according to the present invention will be described with reference to FIG. FIG. 10 shows a configuration of a second embodiment of the plasma floating particle measuring apparatus according to the present invention. The plasma floating particle measuring apparatus includes a laser illumination optical system 104, a scattered light detection optical system 105, and a signal processing / control system 103.
[0034]
In the second embodiment, in order to distinguish the scattered light by the two beams, the foreign matter scattered light is detected by wavelength separation using lasers of different wavelengths. At this time, as in the first embodiment, the intensity of the beam is modulated and the synchronous detection detection method is used in combination to separate and detect the laser scattered light from the plasma emission in both the wavelength and frequency regions.
Laser light source that emits laser light having different wavelengths such as solid laser light (excited by a semiconductor laser) of 532 nm, He—Ne laser light of 633 nm, Ar laser light of 514.5 nm, semiconductor laser light of 780 nm, etc. The P or S polarized beams emitted from 8 and 9 are made incident on the intensity modulators 11 and 12. The intensity modulators 11 and 12 can be composed of an AO (Acousto-Optical) modulator or a mechanical intensity modulator configured to rotate a disk having an opening at high speed. For example, the AO modulator as the intensity modulators 11 and 12 is different from the frequency of plasma emission output from the oscillator 13 based on the control signal 120 from the computer 55, for example, a frequency of 300 kHz and a duty of 40 to 60% (preferably 50%) square wave signal is applied, so that the incident P or S polarized beam is intensity modulated at this frequency. As the frequency whose intensity is modulated, for example, about 300 kHz which is different from the plasma excitation frequency and its harmonic component is used. The polarization of the beam is P or S polarization. Each of the two intensity-modulated beams 603 and 604 is reflected by the mirrors 15 and 16 and expanded by the beam expander 150, and the expanded beam is about a diameter having a very deep depth of focus by the optical system 160. It is converted into spot beams 603 and 604 of about 10 μm to 30 μm.
[0035]
After adjusting the optical axes of the two beams 603 and 604 to make the parallel beams 603 and 604 close to each other, the light passes through or reflects the polarization beam splitter 17 and is reflected by the galvanometer mirror 18, and is reflected from the observation window 7 such as quartz. 1 is irradiated. By rotating the galvanometer mirror 51, the laser beam is scanned over the entire surface of the substrate 4 to be processed. As in the first embodiment, the laser beam passes near the plasma sheath interface immediately above the substrate 4 to be processed such as a semiconductor wafer.
In the scattered light detection optical system 105, the S or P polarized component of the non-polarized scattered light from the processing chamber is reflected or transmitted by the polarization beam splitter 17 through the quartz window 7, and the imaging lens 19 such as quartz is made of quartz or the like. An image is formed on the incident end 20 of the optical fiber 31. As shown in FIGS. 6 and 7, as in the first embodiment, the incident end 20 of the optical fiber 31 is connected to an arbitrary point on the substrate 4 to be processed that connects the point 60 on the optical axis and the incident end 20 of the optical fiber 31. By providing an area 65 capable of receiving scattered light from a point, a floating minute foreign matter scattering signal from an arbitrary point on the substrate to be processed 4 can be detected. Therefore, in combination with the two beams 603 and 604, uniform energy illumination and uniform sensitivity detection can be performed on the floating minute foreign matter 209 over the entire surface of the substrate 4 to be processed.
[0036]
The tip of the fiber 31 is divided into two parts, each connected to a monochromator 40 and a monochromator 41 set to the wavelength of two lasers, and the scattered light by the two laser lights is wavelength-separated, Photoelectric conversion is performed by the photoelectric conversion elements 42 and 43. The light emission signals photoelectrically converted by the photoelectric conversion elements 42 and 43 are amplified by current-voltage conversion amplifiers (amplifiers) 44 and 45 each having a sufficiently higher band than the modulation frequency, and input to the lock-in amplifiers 46 and 47. . Lock-in amplifiers 46 and 47 synchronously detect each input signal using the modulation signal from the oscillator 13 as a reference signal. In this way, the laser scattered light of each wavelength is detected separately from the plasma emission. Thereafter, the same processing as in the first embodiment is performed on the output signals of the lock-in amplifiers 46 and 47.
According to the second embodiment, the plasma processing chamber 1 is irradiated with two beams 603 and 604 having different wavelengths and intensity-modulated at the same frequency as the first embodiment, Two signals based on weak scattered light generated from minute foreign matter 209 floating in or near the plasma 208 are detected, and large background noise such as inner wall scattered light is removed using the detected two signals, for example, integration. By processing and enlarging in time, by selectively extracting only the signal due to the scattered light particles, it is possible to selectively detect only the signal due to the scattered light particles, improving detection sensitivity. However, it is possible to detect a sub-micron-order minute foreign substance floating in or near the plasma, which is expected to be difficult to detect by the conventional method.
[0037]
In the first embodiment, when the detected laser scattered light is separated into two frequency components, a high frequency component common to the modulation frequencies of 300 kHz and 500 kHz, for example, a 1.5 MHz component cannot be completely removed. It will be mixed slightly into the lock-in amplifier output. On the other hand, in the second embodiment, since the scattered light by the two beams is separated with respect to the wavelength, the above-described crosstalk hardly occurs as long as the wavelength difference is 100 nm or more.
In the second embodiment, two beams are used. However, it is possible to use three or more beams. In that case, if the signal processing shown in the first embodiment is performed using scattered signals from adjacent beams, the scanning range of each beam can be narrowed, so that the substrate to be processed is compared with the second embodiment. The time required to scan the entire surface of the (wafer) can be shortened. Also, by increasing the number of beams, it is possible to inspect the entire wafer surface almost simultaneously.
[0038]
Next, a third embodiment of the plasma floating particle measuring apparatus according to the present invention will be described with reference to FIG. FIG. 11 shows the configuration of a third embodiment of the plasma floating particle measuring apparatus according to the present invention. This plasma floating particle measuring apparatus includes a laser illumination optical system 106, a scattered light detection optical system 105, and a signal processing / control system 103.
In the third embodiment, when the scattered light from the two beams is separated and detected, the advantages of the two embodiments are utilized, and beams of different wavelengths and modulation frequencies are used to separate the wavelength and frequency, respectively. It detects scattered light.
Laser beams oscillated from lasers 8 and 9 having different wavelengths are both P or S-polarized light, pass through AO modulators 11 and 12, respectively, and are modulated at different frequencies by oscillators (signal generators) 13 and 14. . As these modulation frequencies, frequencies of 300 kHz and 500 kHz different from the plasma excitation frequency and its harmonic components are used.
[0039]
The two laser beams 605 and 606 having different wavelengths and modulation frequencies are reflected by the mirrors 15 and 16, respectively, the optical axes of the two laser beams 605 and 606 are adjusted, and are converted into close parallel beams. Is reflected or reflected by the galvanometer mirror 18 and irradiated from the observation window 7 to the processing chamber 1. By rotating the galvanometer mirror 18, the laser beam is scanned over the entire surface of the substrate (semiconductor wafer) 4 to be processed. The laser beam passes near the boundary surface of the plasma sheath directly above the substrate 4 to be processed.
In the scattered light detection optical system 105, the S or P polarized component of the non-polarized scattered light from the processing chamber obtained through the observation window 7 is reflected or transmitted by the polarization beam splitter 17, and the imaging lens 19 An image is formed on the incident end 20. As in the first and second embodiments, scattered light from a point on the wafer on the optical axis connecting the incident end 20 of the optical fiber 31 to a certain point 60 on the optical axis and the incident end 20 of the optical fiber 31 is reflected. By providing an area capable of receiving light, a floating minute foreign matter scattering signal from an arbitrary point on the wafer can be detected.
The tip of the fiber 31 is divided into two parts, each connected to a monochromator 40 and a monochromator 41 set to the wavelength of two lasers, and the scattered light by the two laser lights is wavelength-separated, Photoelectric conversion is performed by the photoelectric conversion elements 42 and 43. The light emission signals photoelectrically converted by the photoelectric conversion elements 42 and 43 are amplified by amplifiers 44 and 45 each having a sufficiently higher band than the modulation frequency, and the modulation signals of the oscillators 13 and 14 are respectively converted by the lock-in amplifiers 46 and 47. Each input signal is synchronously detected as a reference signal. Thereafter, the output signals of the lock-in amplifiers 46 and 47 are processed in the same manner as in the first embodiment to eliminate the background noise, so that only the foreign substance scattered signal can be extracted.
[0040]
According to the third embodiment, the plasma processing chamber 1 is irradiated with two beams 605 and 606 having different wavelengths and intensity-modulated at different frequencies from the first embodiment, Two signals based on weak scattered light generated from minute foreign matter 209 floating in or near the plasma 208 are detected, and large background noise such as inner wall scattered light is removed using the detected two signals, for example, integration. By processing and enlarging in time, selectively extracting only the signal from the scattered floating foreign matter scattered light, and selectively observing only the signal from the scattered floating foreign matter scattered light with an improved S / N ratio. As a result, it is possible to detect a sub-micron-order fine foreign substance floating in or near the plasma, which is expected to be difficult to detect by the conventional method.
In addition, the scattered light from the foreign matter is separated from the plasma emission in two regions of wavelength and frequency, and the scattered light from the two beams is also separated from each other in both the region of wavelength and frequency. Compared to the embodiment, the degree of separation of scattered light by the two beams is higher.
[0041]
In the third embodiment, it is also possible to use three or more beams.
[0042]
Next, a fourth embodiment of the plasma floating particle measuring apparatus according to the present invention will be described with reference to FIGS. The fourth embodiment includes a laser illumination optical system 107, a scattered light detection optical system 105, and a signal processing / control system 108. In the first embodiment, the light beams of the two beams 601 and 602 are used. This corresponds to the case where the axes are matched.
The P or S-polarized beam 9 from the laser light source 8 is divided into two by the branching optical element 15a and passed through the AO modulators 11 and 12, respectively, so that the signal generators 13 and 14 in the AO modulators 11 and 12 respectively. Modulated at different frequencies based on the applied signal. As the modulation frequency, for example, 300 kHz or 500 kHz, which is different from the plasma excitation frequency and its harmonic components, is used.
[0043]
The optical axes of the two laser beams 601 ′ and 602 ′ having different modulation frequencies are adjusted and matched by the combining optical element 15 b, then passed through the polarization beam splitter 17, reflected by the galvanometer mirror 18, and transmitted from the observation window 7 to the processing chamber. 1 is irradiated. By rotating the galvanometer mirror 18, the laser beam is scanned over the entire surface of the substrate 4 to be processed. As in the first embodiment, the laser beams 601 ′ and 602 ′ pass through the vicinity of the plasma sheath interface immediately above the substrate to be processed. Reference numerals 16a and 16b denote optical elements to be reflected.
[0044]
In the scattered light detection optical system 102, the S-polarized component of the non-polarized scattered light from the inside of the processing chamber 1 is reflected by the polarizing beam splitter 17 through the observation window 7, and is incident on the incident end 20 of the optical fiber 31 by the imaging lens 19. Make an image. Similar to the first embodiment, the area that can receive scattered light from an arbitrary point on the optical axis connecting the incident end 20 of the optical fiber 31 to a certain point 60 on the optical axis and the incident end 20 of the optical fiber 31. By providing this, it is possible to detect a floating minute foreign matter scattering signal from an arbitrary point on the wafer. The optical fiber 30 is connected to a monochromator 40 set to a laser wavelength, and only the laser scattered light is wavelength-separated from the plasma emission spectrum, and is photoelectrically converted by a photoelectric conversion element 42 such as Photomaru.
The signal photoelectrically converted by the photoelectric conversion element 42 is amplified by an amplifier 44 having a sufficiently higher band than the modulation frequency, and is input to lock-in amplifiers 46 and 47. Lock-in amplifiers 46 and 47 perform synchronous detection using the signals of the signal generators 13 and 14 as reference signals, respectively. The outputs of the lock-in amplifiers 46 and 47 are signals separated from both the wavelength region and the frequency region from the plasma emission.
[0045]
Next, a signal observed when a floating minute foreign substance exists in the plasma processing chamber 1 will be described with reference to FIG. FIG. 13 shows the time change of the output at a certain scanning position on the wafer among the outputs of the lock-in amplifier obtained while scanning the laser beam. FIGS. 13A and 13B show signals by laser beams 601 ′ and 602 ′, respectively. Of the signals 505 and 506, the peak signals 505a and 505b and the peak signals 506a and 506b are scattered signals caused by the same foreign matter. The output level I is due to background noise generated from the wall surface 1W of the processing chamber 1 or the like. Therefore, the foreign matter scattering signals 505a and 506a and 505b and 506b are detected at the same time, while the background noise includes a lot of random electric noise. If the correlation between the signals 505 and 506 is obtained by the correlation processing circuit 54 using these characteristics of both, the correlation coefficient becomes high peaks 507a and 507b when foreign matter is detected, and random background noise becomes a low correlation coefficient. A signal 507 shown in FIG. 13 (c) is obtained. This is the final foreign object detection signal.
[0046]
Therefore, the computer 55 can detect the number of foreign matters by counting the signal 507 generated at the same time shown in FIG. 13C as a floating minute foreign matter scattering signal. That is, the computer 55 can calculate the number of minute foreign matters 209 that float in or near the plasma 208 in units of the substrate 4 to be processed. In particular, when calculating the number of minute foreign matter 209 floating in or near the plasma 208 in the unit of the substrate 4 to be processed, the galvano mirror 18 is rotated at a predetermined time interval and two beams are scanned a plurality of times. Also good. In this way, the computer 55 can grasp the generation state of the minute foreign matter 209 floating in or near the plasma 208 in the unit of the substrate 4 to be processed.
According to the fourth embodiment, the plasma processing chamber 1 is irradiated with two beams 601 ′ and 602 ′ whose optical axes modulated at different frequencies coincide with each other and floats in or near the plasma 208. Two signals 505 and 506 based on weak scattered light generated from the foreign material 209 are detected, and these signals 505 and 506 are correlated at the same time by the correlation processing circuit 54, for example, so that a foreign material scattered signal is randomly generated. As a result, it is possible to detect only the scattered light from the foreign matter selectively, with a further improvement in the S / N ratio, and it is expected to be difficult to detect with the conventional method. It is also possible to detect sub-micron minute foreign matter floating in or near the plasma.
[0047]
Also, in the fourth embodiment, if all signals are correlated using three or more beams, it becomes possible to detect the foreign matter scattering signal by discriminating it from a randomly generated noise component. As a result, it is possible to detect floating fine foreign objects with higher accuracy.
[0048]
Next, a fifth embodiment of the plasma floating particle measuring apparatus according to the present invention will be described with reference to FIG. The fifth embodiment includes a laser illumination optical system 109, a scattered light detection optical system 105, and a signal processing / control system 108. In the second embodiment, the light beams of two beams 603 and 604 are used. This corresponds to the case where the axes are matched.
Laser beams from lasers 8 and 9 having different wavelengths are guided to AO modulators 11 and 12, respectively. By inputting the signal of the signal generator 13 to the AO modulators 11 and 12, the two laser beams 603 ′ and 604 ′ are modulated at the same frequency. As the modulation frequency, a frequency of 300 kHz different from the plasma excitation frequency and its harmonic components is used. The polarization of the beam is P or S polarization.
[0049]
After adjusting the optical axes of the two beams 603 ′ and 604 ′ to make the beams 603 ′ and 604 ′ whose optical axes coincide with each other, the light passes through or reflects through the polarization beam splitter 17 and is reflected by the galvanometer mirror 18 to be observed. 7 is irradiated to the processing chamber 1. By rotating the galvanometer mirror 18, the laser beam is scanned over the entire surface of the substrate 4 to be processed. Similar to the second embodiment, the two laser beams 603 ′ and 604 ′ pass through the vicinity of the plasma sheath interface immediately above the substrate to be processed.
[0050]
In the scattered light detection optical system 105, the S or P polarized component of the non-polarized scattered light from the inside of the processing chamber 1 is reflected or transmitted by the polarizing beam splitter 17 through the observation window 7, and the imaging lens 19 An image is formed on the incident end 20.
The output end of the fiber 31 is divided into two parts and connected to a monochromator 40 and a monochromator 41 set to two laser wavelengths, respectively, and the scattered light by the two laser lights is wavelength-separated, respectively The photoelectric conversion elements 42 and 43 perform photoelectric conversion. The light emission signals photoelectrically converted by the photoelectric conversion elements 42 and 43 are amplified by the amplifiers 44 and 45 each having a sufficiently higher band than the modulation frequency, and the intensity modulation signals from the signal generator 13 are referred to by the lock-in amplifiers 46 and 47. Each input signal is synchronously detected as a signal. In this way, the laser scattered light of each wavelength is detected separately from the plasma emission. Thereafter, processing similar to that in the fourth embodiment is performed to eliminate background noise, thereby detecting minute foreign matters floating in or near the plasma.
According to the fifth embodiment, the plasma processing chamber 1 is irradiated with two beams 603 ′ and 604 ′ having different wavelengths and having the same optical axis modulated at the same frequency. By detecting two signals based on the weak scattered light generated from the minute foreign matter 209 floating in or in the vicinity and correlating these signals, for example, at the same time by the correlation processing circuit 54, the foreign matter scattered signal is randomly determined. It can be detected by discriminating it from the generated noise component, and as a result, only the foreign substance scattered light can be selectively detected with further improvement in the S / N ratio, and it is expected to be difficult to detect by the conventional method. It is also possible to detect sub-micron minute foreign matter floating in or near the plasma.
[0051]
In the fourth embodiment, when the detected laser scattered light is separated into two frequency components, a high frequency component common to the modulation frequencies of 300 kHz and 500 kHz, for example, a 1.5 MHz component cannot be completely removed. It will be mixed slightly into the lock-in amplifier output. For this reason, the correlation coefficient of background noise may increase slightly. On the other hand, in the fifth embodiment, since the scattered light by the two beams is separated with respect to the wavelength, the above-described crosstalk hardly occurs as long as the wavelength difference is 100 nm or more.
[0052]
In the fifth embodiment, two beams are used. However, if all signals are correlated using three or more beams, more accurate foreign object detection is possible.
[0053]
Similarly to the fourth and fifth embodiments, a method in which the optical axes of the two beams are positioned in the third embodiment is also possible.
Next, a sixth embodiment of the plasma floating particle measuring apparatus according to the present invention will be described with reference to FIG. The sixth embodiment includes a laser illumination optical system 110, a scattered light detection optical system 102, and a signal processing / control system 111. In the fourth embodiment, two beams 601'602 'are combined into one. It is a beam. Therefore, for example, P- or S-polarized laser light having a wavelength of 633 nm is irradiated into the plasma processing chamber 1 with an intensity modulation of, for example, 300 kHz, and the synchronously detected foreign matter shown in FIG. A signal of scattered light 242 is output. Then, the DC offset circuit 50 adjusts the DC component to obtain a signal 501 shown in FIG. This signal 501 is A / D converted and stored in the image memory 60. Next, by reading the signal 501 stored in the image memory 60 and delaying it by a delay circuit 61 for a predetermined time, a signal 502 similar to that shown in FIG. 8B can be obtained. Therefore, the computer 55 can obtain the signal 503 from which the noise DC component has been removed by taking the difference between the two signals 501 and 502. Further, the calculator 55 calculates a feature amount indicated by a three-dimensional volume including the gray value of the signal indicating the floating minute foreign matter of the signal 503, and is a signal from the floating minute foreign matter from the calculated feature amount. It becomes possible to recognize whether there is.
[0054]
Further, the computer 55 reads out the signal 501 stored in the image memory 60 and displays it on the display means 58, for example, and a noise component based on scattered reflected light from foreign matter adhering to the side wall 1W of the processing chamber or the observation window 7. Are designated and stored in the storage device 57. Thereby, the computer 55 can discriminate from the waveform due to the floating minute foreign matter by checking the degree of coincidence with the waveform of the noise component.
[0055]
Next, an embodiment in which the plasma floating particle measuring apparatus according to the present invention is introduced into a photolithography process of a semiconductor production line will be described.
[0056]
FIG. 16 shows a photolithography process of the semiconductor production line. First, a film to be processed such as a silicon oxide film is formed on a semiconductor wafer by the film deposition apparatus 301. After the film thickness measurement device 302 measures the film thickness at a plurality of points on the wafer, the resist coating device 303 applies a resist. A desired circuit pattern on the reticle or mask is transferred by the exposure device 304. From the exposed semiconductor wafer, the developing unit 305 removes the resist portion corresponding to the transfer pattern. In the etching apparatus 306, the film to be processed in the resist removing portion is etched using the resist pattern as a mask. Then, the state of the floating minute foreign matter generated in the processing chamber 1 of the etching apparatus is grasped by the plasma floating foreign matter measuring apparatus 100 provided in the etching apparatus at least in units of the substrate 4 to be processed or the lot of the substrate to be processed. When the occurrence state of floating foreign matters (for example, the number of foreign matters) thus grasped exceeds a control value (specified value), the computer 55 notifies the operator using the display means 58 or other output means, and the processing The inside of the chamber 1 is cleaned. If the number of foreign particles does not exceed the specified value, the semiconductor wafer 4 is sent to the cleaning device 308 after the resist film is removed by the ashing device 307 after the etching is completed.
[0057]
In a conventional etching apparatus that does not include a foreign substance detection device in plasma, the contamination status of the etching apparatus is managed by time management, and the processing chamber is not necessarily cleaned at an appropriate time. Therefore, it is possible to reduce the throughput by performing cleaning at a time when it is not necessary to clean, or to reduce the yield by continuing to process a large amount of defective products even though the time to be cleaned has passed. there were. In addition, a method is adopted in which a dummy wafer is inserted and etched in the process, and after processing, the dummy wafer is extracted, foreign matter is inspected to grasp the contamination status, and the cleaning time is determined from the result. In this case, since extra work is performed during the photolithography process, the throughput of the photolithography process is lowered, and the cost of the dummy wafer is put on the photolithography process.
[0058]
According to the present invention, a minute foreign matter floating in or near the plasma is detected by separating the wavelength and frequency domain from the plasma emission, and a large background noise such as inner wall scattered light is removed, and a temporal process by integration processing or the like is performed. By performing an appropriate enlargement process, only the signal due to the scattered light from the foreign substance can be selectively observed with improved S / N, and floating in or near the plasma, which is expected to be difficult to detect by the conventional method. It is also possible to detect minute foreign matters on the order of submicrons.
[0059]
Furthermore, by applying the present invention to an ashing apparatus and a film forming apparatus, real-time monitoring of foreign matter in the ashing apparatus and the film forming apparatus can reduce defects caused by the ashing process and the film forming process during the sography process. Therefore, it is possible to prevent the occurrence of defective products and improve the yield. In addition, the element manufactured by this process is a high-quality element that does not include foreign substances exceeding a specified value.
[0060]
In the above embodiment, 400 kHz is used as the frequency of the plasma excitation high frequency power source, 532 nm and 633 nm are used as the laser wavelengths, and 300 kHz and 500 kHz are used as the laser intensity modulation frequencies. However, the present invention is limited to these values. It is not a thing. In addition, among the above embodiments, in the second and fifth embodiments, it is added that the intensity modulation of the beam is not necessarily required when the scattered light by the two beams is separated and detected using the difference in wavelength. Keep it.
[0061]
Further, the above embodiment is not limited to the parallel plate type plasma etching apparatus as an etching apparatus, but can be applied to various etching apparatuses such as an ECR etching apparatus, a microwave etching apparatus, or a plasma CVD apparatus. Application is also possible.
[0062]
【The invention's effect】
According to the present invention, by detecting weak scattered light generated from floating foreign substances up to submicron in or near the plasma from the plasma emission, the floating foreign substances up to submicron in or near the plasma are detected. The detection sensitivity can be greatly improved. As a result, it is possible to monitor the contamination status in the plasma processing chamber in real time, reduce the occurrence of defective products due to the adhesion of foreign matter, and manufacture high-quality semiconductor elements, etc. with high yield. The effect that becomes possible is obtained.
[0063]
Further, according to the present invention, it is possible to detect minute foreign matters floating in or near the plasma separately from both the wavelength and frequency from the plasma emission, and further obtain two detection signals indicating the fine foreign matters. Thus, it is possible to remove large background noise such as inner wall scattered light and selectively detect only the signal due to the scattered light with improved S / N. As a result, the foreign matter detection sensitivity is improved, and the plasma or There is an effect that it is possible to detect a sub-micron-order minute foreign matter floating in the vicinity thereof.
[0064]
In addition, according to the present invention, a minute foreign substance floating in or near the plasma is detected by separating the wavelength and frequency domain from the plasma emission, and a plurality of beams having different wavelengths or intensity modulation frequencies are irradiated. Then, by extracting a plurality of detection signals based on scattered light from the floating minute foreign matter, and performing a time expansion process such as an integration process based on the time lag of the extracted detection signals, the foreign matter scattering Only light can be selectively magnified and observed.
[0065]
In addition, according to the present invention, a minute foreign substance floating in or near the plasma is detected by separating the wavelength and frequency domain from the plasma emission, and a plurality of beams having different wavelengths or intensity modulation frequencies are irradiated. Then, by extracting a plurality of detection signals based on scattered light from the floating minute foreign matter and correlating the extracted detection signals, only the foreign matter scattered light can be selectively emphasized and observed. .
[0066]
Further, according to the present invention, the laser irradiation optical system and the scattered light detection optical system can be detected by separating the weak backscattered light generated from the suspended foreign matter up to submicron in or near the plasma from the plasma emission. The detection sensitivity of floating foreign substances up to submicron in or near the plasma can be greatly improved. As a result, real-time monitoring of the contamination status in the plasma processing chamber is possible, resulting in defective products due to foreign matter adhesion. The generation of high-quality semiconductor elements and the like can be obtained with a high yield.
[0067]
In addition, according to the present invention, there is an effect that it is possible to accurately grasp the cleaning time of the plasma processing apparatus.
[0068]
Further, according to the present invention, since the frequency of the foreign substance advance check work using the dummy wafer can be reduced, the effects of cost reduction and productivity improvement can be obtained.
[0069]
Further, according to the present invention, there is an effect that the entire production line can be automated.
[0070]
In addition, according to the present invention, when applied to an ashing apparatus or a film forming apparatus, real-time monitoring of foreign matter in the ashing apparatus and the film forming apparatus can be performed, so that defects caused by the ashing process and the film forming process in the sography process can be eliminated. Therefore, it is possible to prevent the occurrence of defective products and improve the yield.
[Brief description of the drawings]
FIG. 1 is a front view showing a first embodiment of a plasma floating particle measuring apparatus provided in a plasma processing apparatus according to the present invention.
FIG. 2 is a diagram showing a relationship between time observed for plasma emission and emission intensity [V].
FIG. 3 is a diagram showing the relationship between frequency [MHz] and emission intensity [mV] observed with a spectrum analyzer for plasma emission.
FIG. 4 is a diagram showing the relationship between the wavelength [nm] / frequency [kHz] of plasma emission in the wavelength and frequency range and the wavelength / frequency of foreign matter scattered light.
FIG. 5 is a plan view showing a first embodiment of a plasma floating particle measuring apparatus provided in a plasma processing apparatus according to the present invention.
FIG. 6 is a diagram showing an imaging relationship of the scattered light detection system in the first to fifth embodiments of the plasma floating particle measuring apparatus according to the present invention.
FIG. 7 is a view showing a light receiving surface of an optical fiber in first to fifth embodiments of the plasma floating particle measuring apparatus according to the present invention.
FIG. 8 is a diagram showing scattered light detection intensity by each beam, a subtraction waveform thereof, and a foreign substance detection signal in the first to third embodiments of the plasma floating foreign substance measuring apparatus according to the present invention.
FIG. 9 is a diagram showing scattered light detection intensity by each beam and its correlation, that is, a foreign matter detection signal in the first to third embodiments of the plasma floating foreign matter measuring apparatus according to the present invention.
FIG. 10 is a plan view showing a second embodiment of the plasma floating particle measuring apparatus provided in the plasma processing apparatus according to the present invention.
FIG. 11 is a plan view showing a third embodiment of the plasma floating particle measuring apparatus provided in the plasma processing apparatus according to the present invention.
FIG. 12 is a plan view showing a fourth embodiment of the plasma floating particle measuring apparatus provided in the plasma processing apparatus according to the present invention.
FIG. 13 is a diagram showing scattered light detection intensity by each beam and its correlation, that is, a foreign matter detection signal in the fourth and fifth embodiments of the plasma floating foreign matter measuring apparatus provided in the plasma processing apparatus according to the present invention. .
FIG. 14 is a plan view showing a fifth embodiment of the plasma floating particle measuring apparatus provided in the plasma processing apparatus according to the present invention.
FIG. 15 is a plan view showing a sixth embodiment of the plasma floating particle measuring apparatus provided in the plasma processing apparatus according to the present invention.
FIG. 16 is a diagram showing a photolithography process of a semiconductor manufacturing line in which an etching apparatus equipped with a plasma floating particle measuring apparatus according to the present invention is introduced.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Processing chamber, 1W ... Side wall, 4 ... Substrate to be processed (semiconductor wafer), 7 ... Observation window, 8, 9 ... Laser light source, 10 ... Multichannel intensity modulator (AO modulator), 11, 12 ... Intensity modulation (AO modulator), 13, 14 ... Oscillator (signal generator), 15a ... Branching optical element, 15b ... Synthetic optical element, 16a, 16b ... Reflecting optical element, 17 ... Polarizing beam splitter, 18 ... Galvano mirror (scanning means) ), 19 ... Imaging lens, 30, 31 ... Optical fiber, 40, 41 ... Monochromator, 42, 43 ... Photoelectric conversion element, 44, 45 ... Current-voltage conversion amplifier, 46, 47 ... Lock-in amplifier, 52 ... Signal processing circuit (subtraction amplifier circuit) 53... Integration circuit 54... Correlation processing circuit 55 .. calculator 70 .. foreign matter adhesion preventing means 100. 04, 106, 107, 109, 110 ... laser irradiation optical system, 102, 105 ... scattered light detection optical system, 103, 107, 108, 111 ... signal processing / control system, 202 ... upper electrode, 203 ... lower electrode, 205 DESCRIPTION OF SYMBOLS ... High frequency power supply (signal generator), 208 ... Plasma, 209 ... Floating minute foreign matter, 301 ... Film forming device, 302 ... Film thickness measuring device, 303 ... Resist coating device, 304 ... Exposure device, 305 ... Developing device, 306 ... Etching 307 ... ashing device, 308 ... cleaning device.

Claims (16)

Processing chamber to generate plasma, in the method for manufacturing a semiconductor device for manufacturing a semiconductor device by processing the semiconductor substrate by the plasma,
An irradiation optical system that irradiates the processing chamber with a plurality of beams having different wavelengths and modulated with an excitation frequency of the plasma and an integer multiple thereof or a specific frequency different from the emission frequency of the plasma and an integral multiple thereof ; Scattered light detection optical system for separating and receiving scattered light obtained from the processing chamber by a plurality of beams irradiated by the irradiation optical system at the different wavelength components and converting them into a plurality of signals, and the scattered light detection Extracting a specific frequency component whose intensity is modulated from a plurality of signals obtained from an optical system, and detecting a plurality of signals indicating a foreign substance floating in or near the plasma separately from the plasma-based one And suspended in or near the plasma generated in the processing chamber using a plasma floating particle measuring apparatus equipped with a means The method of manufacturing a semiconductor device characterized by measuring things. Processing chamber to generate plasma, in the method for manufacturing a semiconductor device for manufacturing a semiconductor device by processing the semiconductor substrate by the plasma,
An irradiation optical system for irradiating the processing chamber with a plurality of beams having a specific wavelength and intensity-modulated at frequencies different from the excitation frequency of the plasma and its integral multiple or the light emission frequency of the plasma and its integral multiple and different from each other; A scattered light detection optical system that separates scattered light obtained from the processing chamber by the plurality of beams irradiated by the irradiation optical system with the specific wavelength component, and converts the light into a signal, and the scattered light detection optics A foreign substance signal extracting means for separating and detecting a plurality of signals indicating foreign substances floating in or near the plasma by extracting the frequency components different from each other in intensity modulated from a signal obtained from the system. Using the plasma floating particle measuring apparatus provided, the foreign particles floating in or near the plasma generated in the processing chamber are measured. The method of manufacturing a semiconductor device, characterized by. The manufacturing method according to claim 1 or 2 semiconductor device according, plasma floating particle measuring apparatus used above, the noise removing means for removing a noise component from a plurality of signals indicating a suspended foreign matter is detected from the foreign object signal extracting means A method for manufacturing a semiconductor device , further comprising : 3. The method of manufacturing a semiconductor device according to claim 1, wherein the irradiation optical system of the plasma floating particle measuring apparatus used further includes a scanning unit that scans the object to be processed. A method for manufacturing a semiconductor device . 3. The semiconductor device manufacturing method according to claim 1, wherein the scattered light detection optical system of the plasma floating particle measuring apparatus used receives backscattered light obtained from the processing chamber. 4. Manufacturing method . 3. The method of manufacturing a semiconductor device according to claim 1, wherein the scattered light detection optical system of the plasma floating particle measuring apparatus used is irradiated with the irradiation optical system among the scattered light obtained from the processing chamber. A method of manufacturing a semiconductor device, wherein a polarization component different from a polarization beam is received . 3. The semiconductor device manufacturing method according to claim 1, wherein the irradiation optical system of the plasma floating particle measuring apparatus to be used comprises optical axes of a plurality of beams as adjacent parallel axes. Device manufacturing method . 3. The method of manufacturing a semiconductor device according to claim 1 , wherein the irradiation optical system of the plasma floating particle measuring apparatus used has the same optical axes of a plurality of beams. Way . In a plasma processing method of generating plasma in a processing chamber and processing an object to be processed with the plasma,
An irradiation optical system that irradiates the processing chamber with a plurality of beams having different wavelengths and modulated with an excitation frequency of the plasma and an integer multiple thereof or a specific frequency different from the emission frequency of the plasma and an integral multiple thereof ; Scattered light detection optical system for separating and receiving scattered light obtained from the processing chamber by a plurality of beams irradiated by the irradiation optical system at the different wavelength components and converting them into a plurality of signals, and the scattered light detection A foreign substance signal extracting means for separating and detecting a signal indicating a foreign substance floating in or near the plasma from a plurality of signals obtained from the optical system by extracting the specific frequency component whose intensity is modulated, from the plasma. A foreign substance suspended in or near the plasma generated in the processing chamber using a plasma suspended foreign substance measuring apparatus equipped with Plasma processing method characterized by measuring. In a plasma processing method of generating plasma in a processing chamber and processing an object to be processed with the plasma,
An irradiation optical system for irradiating the processing chamber with a plurality of beams having a specific wavelength and intensity-modulated at frequencies different from the excitation frequency of the plasma and its integral multiple or the light emission frequency of the plasma and its integral multiple and different from each other; A scattered light detection optical system that separates scattered light obtained from the processing chamber by the plurality of beams irradiated by the irradiation optical system with the specific wavelength component, and converts the light into a signal, and the scattered light detection optics A foreign substance signal extracting means for separating and detecting a plurality of signals indicating foreign substances floating in or near the plasma by extracting the frequency components different from each other in intensity modulated from a signal obtained from the system. Using the plasma floating particle measuring apparatus provided, the foreign particles floating in or near the plasma generated in the processing chamber are measured. Plasma processing method characterized by. The plasma processing method according to claim 9 or 10, wherein the plasma floating particle measuring apparatus used said further noise removal means for removing noise components from a plurality of signals indicating a suspended foreign matter is detected from the foreign object signal extracting means A plasma processing method comprising: 11. The plasma processing method according to claim 9, wherein the irradiation optical system of the plasma floating particle measuring apparatus to be used further includes scanning means for scanning the beam to be processed. Processing method . The plasma processing method according to claim 9 or 10, wherein said scattered light detection optical system of the plasma floating particle measuring apparatus used above, plasma processing method characterized by receiving the backscattered light resulting from the processing chamber. 11. The plasma processing method according to claim 9, wherein the scattered light detection optical system of the plasma floating particle measuring apparatus used is a polarized beam irradiated by the irradiation optical system among scattered light obtained from the processing chamber. A plasma processing method characterized by receiving a polarization component different from the above. The plasma processing method according to claim 9 or 10, wherein the irradiation optical system of the plasma floating particle measuring apparatus used above, plasma processing method characterized by forming the optical axis of the plurality of beams, parallel axes close . The plasma processing method according to claim 9 or 10, wherein the irradiation optical system of the plasma floating particle measuring apparatus used above, plasma processing method characterized by the optical axis of the plurality of beams are made of the same.

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