JP5756974B2 - Manufacturing method of semiconductor device, measuring method in semiconductor etching process - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device or a measurement method in a semiconductor etching process.

  The applicant has applied for an idea to reduce RIE-lag by combining a real-time monitoring technique based on emission spectroscopy and a feedback control technique in the Si deep etching technique (see Japanese Patent Application No. 2010-78251).

  In Si deep etching, a Si substrate with a mask material formed on the surface is etched to form a trench, a protective film is formed on the wall surface of the trench (protective film forming step), and after removing the protective film on the bottom of the trench, the trench The Si substrate is etched again until the side wall surface protective film is removed (etching step). As described above, the etching step has substantially two stages, so that the etching in the depth direction proceeds anisotropically. In other words, etching is performed only in the depth direction between the removal of the protective film on the bottom surface and the removal of the protective film on the side wall surface even in the etching reaction between Si and F atoms having isotropic etching characteristics. As a result, the anisotropy can be maintained. Then, a deep trench is formed in the Si substrate by repeatedly performing the protective film forming step and the etching step.

  In this application, it is the point of the invention to detect the timing at which the protective film made of polymer formed on the bottom and side walls of the trench is removed during the process by emission spectroscopic measurement. Control.

FIG. 6 is a diagram showing the temporal transition of the emission intensity of each atom and molecule in the plasma and the process parameter setting in the process of conventional trench formation. As shown in FIG. 6A, the timing at which the bottom surface protective film is removed is detected by detecting the time point (T = t1) when the emission intensity of F atoms decreases from the start of the etching step after the protective film formation step. To do. Further, as shown in FIG. 6 (b), the timing of C ₂ molecules of emission intensity sidewall protective film of the trench by detecting the time (T = t2) be constant level drops are removed after t1 Is detected.

However, when this method is actually implemented, there are the following problems. In the ordinary Si deep etching technique, the process proceeds between the protective film formation step and the minute etching step while switching the introduced gas in units of several seconds. In the protective film forming step, C ₄ F ₈ gas is mainly used, and in the etching step, SF ₆ gas is mainly used.

  Therefore, it takes a certain time for the introduced gas to be completely switched from the end of each step to the start of the next step, and during this period, the two gases are mixed as shown in FIG. 6 (c). It becomes. In addition, the plasma generation conditions in each step are not necessarily the same. For example, as shown in FIG. 6D, the opening state of the pressure control valve and the matching point of the RF power source for plasma generation are step by step switching. It must be changed every time. These adjustments also require a certain time from the start of each step.

  Due to these factors, the plasma state is transient immediately after the start of each step, and is superimposed as a noise component as shown in FIG. Detection may not be possible.

Further, regarding the removal of the protective film formed on the side wall surface, light emission of C ₂ molecules and the like generated by decomposition and recombination at the time of removal of the protective film, that is, at t2 is measured. However, since the C ₄ F ₈ gas introduced in the previous protective film formation step also remains in the reaction chamber, this C ₂ molecule or the like becomes a noise component as described above.

  Under such circumstances, there is a possibility that the removal timing of the protective film on the bottom surface of the trench and the removal timing of the protective film on the side wall surface cannot be measured accurately.

  Therefore, in order to cope with such problems, Patent Document 1 proposes a method of stopping the measurement at a certain time when there is a concern about noise contamination from the start of the etching step and detecting the peak of F atoms after the certain time has elapsed. . Further, Patent Document 2 proposes a method of measuring only an intermediate period to obtain a representative value excluding a certain time and a certain time before the end from the start of the etching step.

In these Patent Documents 1 and 2, the purpose is to detect that the etching front end surface has reached a base film such as SiO ₂ while monitoring the representative value of F atoms during Si etching. The method is to measure after a certain time later.

JP 2001-501041 A JP 2003-92286 A

  However, in Patent Documents 1 and 2 described above, in order to prevent the influence of noise on the measurement result of the light emission intensity, the light emission intensity is measured after a lapse of a certain time after step switching. For this reason, the methods described in Patent Documents 1 and 2 cannot grasp the exact timing at which the protective film on the bottom surface and the side wall surface of the trench is removed.

  The present invention has been made in view of the above points, and it is an object of the present invention to accurately grasp the timing at which the protective film on the bottom surface and side wall surface of the trench is removed.

  In order to achieve the above object, according to the first aspect of the present invention, an Si substrate (19) or an SOI substrate on which a mask material (23) having a predetermined pattern is formed on the surface (19a) is placed in the reaction chamber (10). The substrate is etched in accordance with the pattern of the mask material (23) by causing discharge in the reaction chamber (10) and plasmaizing the introduced gas introduced into the reaction chamber (10) and irradiating the substrate. A protective film in which a protective film (25) is deposited on the wall surface of the trench (24) formed in the substrate by the etching step by switching the introduced gas and causing discharge in the reaction chamber (10) to generate plasma. And a deposition step.

  A method of manufacturing a semiconductor device in which a trench (24) is dug down by repeating an etching step and a protective film deposition step while leaving a mask material (23) on the substrate, and is characterized by the following points. .

  That is, before and after the start of the etching step, the plasma generation discharge is stopped, the introduced gas is completely replaced with the gas corresponding to each step, and the pressure in the reaction chamber (10) is set to a predetermined value. In addition, a switching step for setting the set value of the process parameter to a value corresponding to each step while the discharge is stopped is included.

  In the etching step after the switching step, the intensity change of the characteristic emission peak wavelength that reflects the progress of the etching process of the protective film (25) is monitored by the emission spectrometer (15), and the trench is determined from the monitored waveform. It is characterized by grasping the timing at which the protective film (25) deposited on the bottom surface of (24) is removed and the timing at which the protective film (25) deposited on the side wall surface of the trench (24) is removed.

  According to this, when switching from the protective film deposition step to the etching step, the switching step is executed to completely replace the introduced gas in the reaction chamber (10) with the gas corresponding to the etching step. The reaction chamber (10) is in a stable state. For this reason, the influence of noise does not affect the measurement result of the emission intensity in the etching step. Therefore, the timing at which the protective film (25) deposited on the bottom surface of the trench (24) is removed from the monitored waveform, and the timing at which the protective film (25) deposited on the side wall surface of the trench (24) is removed, respectively. Accurately grasp.

As in the second aspect of the invention, in the etching step, a gas containing F atoms can be used as the introduced gas, and the intensity change of the emission peak wavelength of the F atoms or SiF _x molecules can be monitored.

As in the third aspect of the invention, the protective film deposition step uses a gas containing C atoms as the introduction gas, and the etching step can monitor the intensity change of the emission peak wavelength of C atoms or C ₂ molecules.

In the protective film deposition step, a gas containing O atoms is used as the introduction gas in the protective film deposition step, and the intensity change of the emission peak wavelength of the O atom or SiO _x molecule is monitored in the etching step. You can also.

  The invention according to claim 5 is characterized in that the time for stopping the discharge for plasma generation before and after the start of the etching step is set longer than the time required for replacing the introduced gas or setting the process parameters. . This ensures that a stable state is created in the reaction chamber (10) before proceeding to the etching step.

  According to the sixth aspect of the present invention, a plurality of repetitions of the protective film deposition step and the etching step are performed to grasp the timing at which the protective film (25) is removed by monitoring the intensity change of the emission peak wavelength. The etching is performed in one etching step. Accordingly, it is possible to minimize the increase in the process time due to the repetition of the time for stopping the discharge.

  Although the semiconductor device manufacturing method has been described above, the progress of etching of the protective film (25) in the etching step is monitored using the emission spectrometer (15) as in the inventions of claims 7-12. It can also be employed as a measurement method in a semiconductor etching process.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is a schematic diagram of an etching apparatus according to a first embodiment of the present invention. It is the figure which showed the time transition of each process setting for demonstrating the outline | summary of an etching process. It is the figure which showed an example of the peak of F atom. It is the figure which showed the formation step of a trench. It is the figure which showed the time transition of each process setting which concerns on 1st Embodiment. It is the figure which showed the time transition of each process setting in the conventional trench formation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a method for manufacturing a semiconductor device in which a trench is formed in a semiconductor substrate and a method for measuring emission intensity for grasping the progress of a semiconductor etching process in the manufacturing method will be described. First, the configuration of the etching apparatus used in this embodiment will be described.

  FIG. 1 is a schematic diagram of an etching apparatus according to this embodiment. As shown in this figure, the etching apparatus includes a reaction chamber 10, a plasma generation power supply 11, a bias power supply 12, an etching gas mass flow controller 13, a protective film deposition mass flow controller 14, and an emission spectrometer. 15 is provided.

  The reaction chamber 10 constituting the vacuum chamber is provided with a gas inlet 16 and an exhaust port 17. A mass flow controller 13 for etching gas and a mass flow controller 14 for depositing a protective film are connected to the gas inlet 16. The mass flow controllers 13 and 14 control the flow rates of various gases into the reaction chamber 10.

  An RF coil 18 is built in the reaction chamber 10, and an RF electric field is generated in the reaction chamber 10 by supplying electric power to the RF coil 18 from a power source 11 for generating plasma. Note that a matching device (not shown) is connected to the power source 11. Then, according to each step, the RF matching position (matching point) of the capacitance value of the variable capacitor is changed in accordance with the impedance of the plasma itself.

  Then, the Si substrate 19 to be etched is arranged on the installation table 20 arranged in the reaction chamber 10. The Si substrate 19 is a Si wafer, and a trench is formed on the surface 19 a side of the Si substrate 19. Since the power supply 12 for bias is electrically connected to the installation base 20, a predetermined bias is applied to the Si substrate 19. The installation base 20 has a mechanism in which a cooling He gas for cooling the Si substrate 19 from the back side is introduced.

  Further, an observation window 21 is provided in the reaction chamber 10 above the Si substrate 19. An optical fiber 22 is connected to the observation window 21, and the optical fiber 22 is connected to the emission spectrometer 15. The emission spectrometer 15 monitors the intensity change of the characteristic emission peak wavelength that reflects the progress of the etching process. The above is the configuration of the etching apparatus.

  Next, an outline of a trench forming method for the Si substrate 19 will be described. The trench forming method will be briefly described. First, the Si substrate 19 having a mask material formed on the surface 19a is set in the reaction chamber 10. Subsequently, the Si substrate 19 is etched in accordance with the pattern of the mask material by causing discharge in the reaction chamber 10 to be plasma and irradiating the Si substrate 19 with the introduced gas introduced into the reaction chamber 10 (etching step). Thereafter, the introduced gas is switched to cause discharge again in the reaction chamber 10 to turn the introduced gas into plasma, and a protective film is deposited on the wall surface of the trench formed in the Si substrate 19 by the etching step (protective film deposition step). . Then, the trench is dug down by repeating the etching step and the protective film deposition step while leaving the mask material on the Si substrate 19.

And when forming a trench as mentioned above, in this embodiment,
(1) Turn off the plasma generation discharge once the protective film formation step immediately before the etching step is completed. (2) After that, the replacement of the introduced gas in the etching step, the transition of process parameters, etc. are completely completed. Then, the discharge is resumed and the etching step is started.

  FIG. 2 is a time transition of process settings showing (a) flow gas, (b) plasma generation RF value, (c) pressure control valve opening degree, and (d) emission intensity with respect to the time axis. . Note that the “plasma generation RF value” in FIG. 2B is the input power of the power source 11 for plasma generation.

  When the protective film deposition step ends at the time point T = T1, the supply of the gas introduced into the reaction chamber 10 in the protective film deposition step is stopped as shown in FIG. Is replaced with the introduced gas for the etching step. Further, as shown in FIG. 2B, the plasma generation RF value is set to “0” at time T1, and the discharge is turned off. Further, as shown in FIG. 2C, the opening of the pressure control valve is adjusted for the etching step. Other process parameter setting values are also changed for the etching step. Since no reaction caused by the discharge occurs in the reaction chamber 10, the emission intensity observed by the emission spectrometer 15 becomes zero as shown in FIG.

  Thereafter, the power source 11 for generating plasma is turned on from the time T = T2, and discharge is caused again in the reaction chamber 10 to start the etching step. Note that the introduced gas and process parameters are changed after the etching step in the same manner as described above.

  Here, a period from time T1 to time T2 when the discharge is turned off is defined as a switching step. That is, in the switching step, the discharge for plasma generation is stopped, the introduced gas is completely replaced with the gas corresponding to each step, the pressure in the reaction chamber 10 is set to a predetermined value, and the discharge is stopped. In the meantime, the set value of the process parameter is set to a value corresponding to each step. The switching step is provided before and after the start of the etching step, that is, between the protective film deposition step and the etching step, and between the etching step and the protective film deposition step.

  As described above, the reaction chamber 10 after the etching step is started is not in a transient state, but is discharged after a steady state is started to start the etching step. The transient state is a state in which the introduced gas used in the previous step is left in the reaction chamber 10, and the steady state is a state in which only the introduced gas used in the current step exists in the reaction chamber 10. Thus, it was experimentally confirmed that the protective film removal timing can be accurately detected without being affected by the noise described above.

  FIG. 3 is an example of measuring the peak of F atoms. Without using the above technique, if the emission intensity is measured by a method including a transient state, such as a protective film formation step → etching step →..., The influence of noise or the like is affected as shown in FIG. In response, the stepped waveform of the F atom may be crushed or the reproducibility of the measurement will be reduced. Further, when the etching progresses and the trench becomes deep, the measurement waveform is distorted as a whole and accurate timing detection cannot be performed.

  On the other hand, it was found that by using the above-described method, as shown in FIG. 3B, waveform collapse and distortion are eliminated, and measurement reproducibility can be obtained. Further, when the etching progresses and the trench becomes deep, the entire measurement waveform is not distorted, and an accurate timing for removing the protective film can be detected even for the deep trench. Note that the timing of removing the protective film can be grasped by detecting that the emission intensity is below the detection threshold as shown in FIG.

  Next, specific trench formation will be described with reference to FIGS. As described above, in the normal Si deep etching, after the Si substrate 19 to be etched is placed in the reaction chamber 10, the protective film deposition step and the etching step are performed for several seconds, specifically 2 seconds to 10 seconds. Perform alternately at a degree.

First, a surface of the Si substrate 19 on which an appropriately patterned SiO ₂ mask material 23 is formed is prepared and placed on the stage 20 of the reaction chamber 10. Then, as shown in FIG. 4A, first, an etching step is performed to form a trench 24 in the Si substrate 19.

Next, a protective film deposition step is performed. Introducing a mixed gas of only _C 4 _{F 8} gas as a protective film deposition step shown in FIG. 5 (a), or _C 4 _{F 8} gas and some additive gas (Ar or _{O 2,} etc.) into the reaction chamber 10 To do. The flow rate is several hundred sccm, specifically about 100 sccm to 500 sccm, and the pressure in the reaction chamber 10 during the process is about 1 Pa, specifically about 1 Pa to 10 Pa. Then, the introduced gas introduced into the reaction chamber 10 is turned into plasma by inputting the plasma generation power supply 11 at a constant power. The power source 11 for generating plasma is, for example, one having a frequency of 13.56 MHz, and the input power is about several hundred W to several kW. As a result, CF _x (x = 0 to 4) is generated and a polymerization reaction is caused on the surface 19a of the Si substrate 19 to form a fluorocarbon-based polymer film. This polymer film is the protective film 25 shown in FIG.

  After performing this protective film deposition step for a predetermined time, as shown in FIG. 5B, the plasma generation power source 11 is temporarily turned off at time T1, and the process proceeds to the switching step. Here, normally, in the Si deep etching apparatus, two RF power sources, that is, a plasma generating power source 11 and a bias applying power source 12 are used, but when the plasma generating power source 11 is turned off, the bias applying power source 12 is used. Is also OFF.

Next, in order to perform the etching step, the introduced gas is switched, and SF ₆ gas or a mixed gas of SF ₆ gas and some additive gas (Ar, O _2, etc.) is introduced into the reaction chamber 10. The flow rate is several hundred sccm, specifically about 100 sccm to 500 sccm, and the pressure in the reaction chamber 10 during the process is about 1 Pa, specifically about 1 Pa to 10 Pa. It takes about 1 second to several seconds for the introduced gas in the reaction chamber 10 to be completely replaced. Thereafter, the pressure in the reaction chamber 10 is stabilized at an appropriate set value.

  Further, in the switching step, as shown in FIG. 5C, the valve opening degree for adjusting the chamber pressure and the matching point of the plasma generation power source 11 also change toward the set values at the time of performing the etching step. Note that the process parameter setting values in the etching step are not necessarily the same as the setting values in the protective film deposition step.

  Thereafter, the etching step is started from time T2 in FIG. That is, the plasma generation power source 11 is turned on again to cause a discharge in the reaction chamber 10 to turn the introduced gas into plasma. Also, the power supply 12 for bias application is turned on. The bias applying power source 12 has, for example, a frequency of about 13.56 MHz or several hundreds of kHz, and has an input of several tens of watts to several hundreds of watts.

  In the etching step after time T2, light emission from the plasma generated in the reaction chamber 10 is collected from the observation window 21 and introduced into the emission spectrometer 15 via the optical fiber 22. Here, as shown in FIG. 5D, the intensity is measured after being divided into each wavelength component.

When the etching step is started and the protective film 25 (polymer film) on the bottom surface of the trench 24 formed in the immediately preceding protective film deposition step is removed and the Si etching reaction starts, the F atom concentration in the SF ₆ plasma is increased. descend. For this reason, the intensity of the emission peak (for example, λ = 685.6 nm) due to the F atom is lowered. On the other hand, the intensity of the emission peak (for example, λ = 777.0 nm) due to SiF _x molecules generated by the reaction product (SiF ₄ ) in the etching reaction being dissociated again in the plasma increases.

  Then, when shifting from the protective film deposition step to the etching step, the introduced gas used in the protective film deposition step and the introduced gas used in the etching step are completely switched. For this reason, the decrease or increase in the peak intensity does not include a noise component due to the transient state, and can be observed very clearly.

  From this change in peak intensity, as shown in FIG. 4C, the time point (T = t1) at which the protective film 25 on the bottom surface of the trench 24 is completely removed can be detected, and this is used as a trigger signal. As shown in FIG. 5B, for example, feedback control for reducing the set value of the power supply 12 for bias application can be performed.

As shown in FIG. 5D, since the time t1 at which the peak intensities of the F atom and the SiF _x molecule change is the same, by detecting the time t1 from these two peak intensities, the trench 24 is detected. It is possible to accurately grasp the timing at which the protective film 25 on the bottom surface is completely removed.

In addition, it is considered that a light emission peak (for example, λ = 516.5 nm) due to C ₂ molecules is generated by re-dissociation, bonding, or the like in plasma when the protective film 25 is decomposed and removed. Therefore, the protective film 25 on the bottom surface of the trench 24 and further on the side wall surface gradually disappears due to the etching action, and finally the peak intensity gradually decreases until the protective film 25 on the side wall surface is completely removed. Become. Alternatively, the emission intensity of the peak of the F atom shows a second decrease. This is because the introduced gas is after being completely replaced with SF ₆ , so that C ₂ molecules are generated only from the decomposition of the protective film 25. These timings can be grasped as the side wall protective film removal timing. When the protective film 25 on the side wall surface of the trench 24 is removed, the trench 24 becomes deeper as shown in FIG.

  When the protective film 25 on the side wall surface of the trench 24 is removed, T = t2, and this can be used as a trigger signal to complete the etching step, for example. As described above, the timing at which the protective film 25 deposited on the bottom surface of the trench 24 is removed from the waveform monitored by the emission spectrometer 15 (T = t1), and the protective film 25 deposited on the sidewall surface of the trench 24 The removed timing (T = t2) can be accurately grasped.

In the switching step, feedback control can be performed to change the setting values of the introduced gas and each process parameter so as to return to the protective film deposition step again. Such feedback control makes it possible to improve the etching rate, improve the mask selection ratio, or suppress the RIE-lag described above. Thus, since there is a period of switching the step stopping the discharge when moving to the protective film deposition step from the etching step, the timing of the peak of C ₂ molecule becomes a constant value due to noise in the transient state is buried in noise Can be prevented.

  Here, the time during which the discharge is turned off before and after the etching step is set longer than the time necessary for the replacement of the introduced gas or the transition of the valve opening or RF matching point. Specifically, it is about 1 second to 2 seconds. As a result, a stable state can be reliably created before shifting to each step.

(Second Embodiment)
In the present embodiment, parts different from the first embodiment will be described. As described above, in the etching technique in which the trench 24 is dug by repeating the protective film deposition step and the etching step, the polymer film is formed as the protective film 25 in the first embodiment. However, in the present embodiment, the protective film 25 is formed. As a result, an SiO ₂ film is formed by O ₂ plasma irradiation. Also in this embodiment, the etching manufacturing apparatus shown in FIG. 1 is used.

Also in this case, once the protective film deposition step for forming the SiO ₂ film is completed, the discharge by the power source 11 for plasma generation is once stopped, and the SF ₆ in the next etching step is switched to the main gas to complete the process. Replace with. Then, after the chamber pressure is stabilized and the change of various process parameter setting values in the etching step is completed during this time, the power source 11 for plasma generation is turned on again.

Thus, when the SiO ₂ film on the bottom surface of the trench 24 is removed and Si etching starts, the emission intensity of F atoms decreases and the emission intensity of SiF _x molecules increases as in the first embodiment. Can be detected. This detection timing can be accurately grasped as the timing at which the SiO ₂ film on the bottom surface of the trench 24 is removed.

Thereafter, while the SiO ₂ film on the sidewall surface of the trench 24 is removed, it is observed that the peak of the emission intensity of SiO _x molecules or the emission intensity peak due to O atoms gradually decreases. This state is the same as the peak of the emission intensity of the C ₂ molecule shown in the first embodiment. The time point at which these emission intensity peaks decrease and become a constant value is set as a reference, and when this peak is reached, the timing at which the SiO ₂ film on the sidewall surface of the trench 24 is removed can be detected. This detection timing can be accurately grasped as the timing at which the SiO ₂ film on the side wall surface of the trench 24 is removed.

(Other embodiments)
The trench formation methods described in the above embodiments are merely examples, and the present invention is not limited to the methods described above, and other configurations that can realize the present invention may be employed. For example, it is not always necessary to stop the discharge at every cycle and monitor the light emission intensity, and may be omitted in a form that is performed once for the execution of a plurality of etching steps within a range allowed for accuracy of feedback control. . This is to minimize the increase in process time due to repeated switching steps, ie, the discharge OFF time.

In each of the above embodiments, a method of forming only one protective film 25 is shown. However, a polymer film is formed as the first protective film, and SiO ₂ formed by O ₂ plasma irradiation is formed thereon as the second protective film. A method of forming _two films is known. In this method, after the SiO ₂ film as the second protective film is formed, the process returns to the repetition of the protective film deposition step and the etching step with the normal polymer film as the first protective film. Therefore, there are two cases where the protective film deposition step is performed first after the SiO ₂ film is formed and the etching step is performed first. However, in either case, since there is a switching step in which the plasma generation power supply 11 is turned off and gas is completely replaced before the etching step is started, emission spectroscopy is performed while the plasma generation power supply 11 is turned on again. Even if measurement is performed, there is no influence of noise.

  Further, in each of the above embodiments, the Si substrate is used as a substrate for forming the trench 24. However, the trench 24 may be formed in an SOI substrate in which an insulating layer is sandwiched between two Si substrates.

DESCRIPTION OF SYMBOLS 10 Reaction chamber 15 Emission spectrometer 19 Si substrate 19a Surface 23 Mask material 24 Trench 25 Protective film

Claims (12)

A Si substrate (19) or SOI substrate on which a mask material (23) having a predetermined patterning is formed on the surface (19a) is placed in the reaction chamber (10), and discharge is caused in the reaction chamber (10). An etching step of etching the substrate according to the pattern of the mask material (23) by converting the introduced gas introduced into the reaction chamber (10) into plasma and irradiating the substrate with the plasma;
Protective film deposition in which the introduced gas is switched to generate plasma by causing discharge in the reaction chamber (10), and a protective film (25) is deposited on the wall surface of the trench (24) formed in the substrate by the etching step. Steps, and
A method of manufacturing a semiconductor device in which the trench (24) is dug down by repeating the etching step and the protective film deposition step while leaving the mask material (23) on the substrate,
Before and after the start of the etching step, the discharge for plasma generation is stopped, and the introduced gas is completely replaced with a gas corresponding to each step, and the pressure in the reaction chamber (10) is set to a predetermined value. A switching step for setting and setting a process parameter setting value to a value corresponding to each step while the discharge is stopped is included,
In the etching step after the switching step, the intensity change of the characteristic emission peak wavelength reflecting the progress of the etching process of the protective film (25) is monitored by the emission spectrometer (15), and from the monitored waveform, The timing at which the protective film (25) deposited on the bottom surface of the trench (24) is removed and the timing at which the protective film (25) deposited on the side wall surface of the trench (24) is removed are grasped. A method for manufacturing a semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a gas containing F atoms is used as an introduction gas in the etching step, and intensity change of an emission peak wavelength of the F atoms or SiF _x molecules is monitored. In the protective film deposition step, a gas containing C atoms is used as an introduction gas,
_{2. The} method of manufacturing a semiconductor device according to claim 1, wherein in the etching step, an intensity change of an emission peak wavelength of the C atom or C2 molecule is monitored. In the protective film deposition step, a gas containing O atoms is used as the introduction gas as the introduction gas,
2. The method of manufacturing a semiconductor device according to claim 1, wherein in the etching step, an intensity change of an emission peak wavelength of the O atom or SiO _x molecule is monitored.   5. The time for stopping the discharge for generating the plasma before and after the start of the etching step is set longer than the time required for replacing the introduced gas or setting the process parameters. The manufacturing method of the semiconductor device as described in any one of these.   As for grasping the timing at which the protective film (25) is removed by monitoring the intensity change of the emission peak wavelength, one of repeating the protective film deposition step and the etching step a plurality of times. 6. The method of manufacturing a semiconductor device according to claim 1, wherein the method is performed in a single etching step. A Si substrate (19) or SOI substrate on which a mask material (23) having a predetermined patterning is formed on the surface (19a) is placed in the reaction chamber (10), and discharge is caused in the reaction chamber (10). An etching step of etching the substrate according to the pattern of the mask material (23) by converting the introduced gas introduced into the reaction chamber (10) into plasma and irradiating the substrate with the plasma;
Protective film deposition in which the introduced gas is switched to generate plasma by causing discharge in the reaction chamber (10), and a protective film (25) is deposited on the wall surface of the trench (24) formed in the substrate by the etching step. Steps, and
When the trench (24) is dug down by repeating the etching step and the protective film deposition step while leaving the mask material (23) on the substrate, the protective film (25) in the etching step A measuring method in a semiconductor etching process for monitoring the progress of etching using an emission spectrometer (15),
Before and after the start of the etching step, the discharge for plasma generation is stopped, and the introduced gas is completely replaced with a gas corresponding to each step, and the pressure in the reaction chamber (10) is set to a predetermined value. A switching step for setting and setting a process parameter setting value to a value corresponding to each step while the discharge is stopped is included,
Characteristic light emission reflecting the progress of the etching process of the protective film (25) until the plasma generation discharge is restarted and the etching step is started, and the discharge is stopped again and the etching step is completed. The intensity change of the peak wavelength is monitored by the emission spectrometer (15), and the timing at which the protective film (25) deposited on the bottom surface of the trench (24) is removed from the monitored waveform, and the trench (24) A measurement method characterized by grasping the timing at which the protective film (25) deposited on the side wall surface of the substrate is removed. The measurement according to claim 7, wherein in the etching step, a gas containing F atoms is used as an introduction gas used in the etching step, and an intensity change of an emission peak wavelength of the F atoms or SiF _x molecules is monitored. Method. 8. In the protective film deposition step, a gas containing C atoms is used as an introduction gas used in the protective film deposition step, and a change in emission peak wavelength intensity of the C atoms or C ₂ molecules is monitored. Measurement method described in 1. In the protective film deposition step, a gas containing O atoms is used as an introduction gas as an introduction gas used in the protection film deposition step, and the intensity change of the emission peak wavelength of the O atoms or SiO _x molecules is monitored. The measurement method according to claim 7.   11. The time for stopping the plasma generation discharge before and after the start of the etching step is set longer than the time required for replacing the introduced gas or setting the process parameters. The measuring method as described in any one of these.   As for grasping the timing at which the protective film (25) is removed by monitoring the intensity change of the emission peak wavelength, one of repeating the protective film deposition step and the etching step a plurality of times. The measurement method according to claim 7, wherein the measurement is performed in a single etching step.

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