JPH08106992A - Plasma processing method and its device - Google Patents

Abstract

PURPOSE: To stably and accurately monitor a spectrum of plasma and an etching reaction product, and maintain etching processing stable for many hours by arranging correcting means in natural lighting windows. CONSTITUTION: A shutter 7 is opened, and reference light of a light source 8 is taken in a spectral analusis part 4, and its spectrum is detected. Next, the shutter 7 is closed, and a shutter 6 is opened, and reference light passing through natural lighting windows 1' and 1 is gathered by the analysis part 4, and its spectrum is detected. Light emitting intensity with respective wave lengths is corrected by an original spectrum of the reference light gathered by the analysis part 4 through the shutter 7 in the spectrum of the light gathered by the analysis part 4 through the windows 1' and 1, and transmissivity of the windows 1' and 1 corresponding to the respective wave lengths is found. Next, the shutter 6 is closed, and the light source 8 is turned off, and plasma is generated in a processing chamber 2. A spectrum of its plasma emitting light is gathered through the window 1, and is corrected by transmissivity of the window 1, and original plasma emitting light is found.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma for processing a wafer, which is a substrate to be processed such as a semiconductor device, by using plasma generated in a vacuum such as dry etching processing, plasma CVD processing, and sputter film forming processing. The present invention relates to a processing method and an apparatus thereof.

[0002]

2. Description of the Related Art In a plasma processing apparatus for processing a semiconductor device using plasma, for example, a dry etching apparatus, a plasma processing chamber (hereinafter, referred to as a vacuum atmosphere) is used.
A processing gas is introduced into a processing chamber (hereinafter simply referred to as a processing chamber) to generate plasma, and ions or radicals (neutral active species) having high chemical reactivity are generated by ionization and dissociation processes of the processing gas. Then, these active particles act physically or chemically to etch away a desired portion of the film to be processed on the semiconductor wafer to form a device pattern. As a means for monitoring the state of this etching process, plasma emission spectroscopy can monitor many factors that affect etching characteristics such as active species level, reaction product level, and leak level, and it does not affect plasma. Widely used.

As a conventional monitoring method using plasma emission spectral analysis, Japanese Patent Laid-Open No. 4-212414 and
There is a method disclosed in JP-A-61-67227.

Japanese Laid-Open Patent Publication No. 4-212414 discloses spectral data of secondary light due to plasma emission or external incident light, potential of electrodes placed on a wafer or plasma, or infrared light transmitted through the wafer. There is disclosed a plasma processing apparatus that controls controllable parameters online so that a desired plasma processing result can be obtained from spectral data.

In the plasma processing apparatus disclosed in Japanese Patent Laid-Open No. 4-212414, in order to perform the above control,
An apparatus control computer stores processing conditions, the above-mentioned spectrum data or potential, and a database showing a correlation result with a prescribed value of the processing result.

In the plasma processing apparatus disclosed in Japanese Patent Laid-Open No. 61-67227, the plasma emission is received by a photo sensor through a transmission window provided in the plasma processing chamber, and the emission intensity of the plasma is constantly measured to detect abnormal emission. There is disclosed a method of detecting an abnormality during etching from an abnormal emission intensity, which is provided with a plasma emission measuring instrument adapted to detect the intensity.

By the way, with the high integration of LSI, high precision is required for its processing. In order to perform high-precision processing, it is of course necessary to improve the performance of each processing equipment, but in order to improve productivity it is important to maintain the performance of each processing equipment stable for a long time and not cause defects. Is.

In the processing apparatus, an etching apparatus that plasmaizes a processing gas in a vacuum container to form a pattern on the wafer surface is examined. During the etching processing, the resist, which is a mask of the pattern, is decomposed to generate organic substances. It adheres to the inner wall of the processing chamber, or the metal (aluminum, molybdenum, or tungsten) that is the material to be etched adheres to the inner wall of the processing chamber as a film. When these deposits come into contact with plasma, gas is generated due to the action of ions in the plasma and the temperature rise of the wall of the processing chamber, and the state of microwaves entering the processing chamber changes due to the adhesion of the metal film. As a result, the plasma state in the processing chamber changes.

Since the etching process is performed by plasma, the etching characteristics also change depending on the change of the plasma state. Furthermore, the O-ring for vacuum sealing is deteriorated by the etching gas, a minute leak is generated, and the plasma state is changed. That is, when the etching apparatus is continuously operated for a long time, the etching characteristics change with time, and eventually the inspection pass condition is not satisfied, leading to the occurrence of defects. Further, the adhered matter on the inner wall of the processing chamber peels off at a certain thickness to become a foreign matter. This is also the case with other plasma processing apparatuses (CVD apparatus, sputtering apparatus, etc.), which is an obstacle to keeping the performance stable for a long time.

So far, for example, Japanese Patent Laid-Open No. 63-4212.
As in the plasma etching apparatus disclosed in Japanese Patent Publication No. 4, the plasma state is monitored by the light emission during the etching process, but the monitoring result is used only for monitoring the end of etching. There is. That is, during etching, the material to be etched (aluminum, etc.) appears in the plasma due to the etching reaction,
The intensity of the light (wavelength peculiar to the substance) emitted by this is monitored, and it is detected that the etching is completed when the intensity of the light becomes zero. Therefore, the time and etching rate required to etch one wafer can be obtained, but even if this value changes, no particular modification to the processing conditions has been made. Moreover, nothing has been done to prevent the occurrence of defects.

[0011]

A problem in spectroscopic analysis of plasma emission is that the window for detecting plasma emission changes with time due to the etching process.

That is, if the window of the processing chamber is left as it is, the reaction product generated by the etching process adheres to the surface in the form of a film, so that the transmittance for plasma emission changes. Also, when the window of the processing chamber is directly exposed to plasma, the surface of the window inside the processing chamber becomes uneven due to the sputtering effect of the plasma, and the light emitted by the plasma and reaching the lighting window is diffusely reflected and transmitted through the lighting window. The amount of light emitted decreases, and the amount of light incident on the spectroscope decreases correspondingly. Due to these factors, it is impossible to distinguish whether the plasma emission amount itself changes or the window transmittance changes even if the plasma emission amount detected by the spectroscope changes. In the conventional plasma processing apparatus for performing the emission analysis monitor, since the transmission characteristics of the plasma light of the plasma monitoring daylighting window as described above are not taken into consideration due to the change over time due to the etching action during the plasma processing, It was difficult to always obtain a constant monitor output for the same plasma emission amount, and it was difficult to always obtain a stable plasma processing result.

Further, the plasma monitoring during the etching process in the above-mentioned prior art does not widely monitor the conditions relating to the etching characteristics, but the contents that can be detected by monitoring are limited to the end point detection and the abnormality detection. .

Further, when the etching process is repeated, reaction products adhere to the inner surface of the processing chamber, which causes a change in plasma state. Since the etching reaction conditions change when the plasma state changes, appropriate etching cannot be performed if the etching conditions are kept constant. Therefore, in order to always perform a constant and stable etching process, it is necessary to frequently clean the reaction chamber to maintain a state in which a constant plasma can be generated. However, in the above-mentioned conventional technique, the monitored plasma emission amount data is used only for the determination of plasma stability and etching characteristics, and no consideration is given to contamination in the processing chamber. For this reason, it is not possible to accurately determine the cleaning time in the processing chamber, and it is not possible to prevent contamination of the processing wafer due to dirt in the processing chamber.

Further, for example, the above-mentioned prior art JP-A-63-
In Japanese Patent No. 42124, only the end of the etching process is monitored, and the result of the etching process (pattern cross-section size, shape, processing wafer in-plane uniformity, etc.) satisfies the inspection pass condition. I have not confirmed that. Therefore, the characteristics of the processing apparatus change, and as a result, even if the etching process fails the inspection conditions, the process is continued under the same conditions, resulting in a defective product. As described in the above-mentioned section of the prior art, since the processing characteristics of the etching processing apparatus change with time, it is necessary to accurately inspect the result every time processing is performed.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to monitor the plasma emission without being affected by the change of the transmission characteristics of the lighting window, and a plasma processing method provided with the same. It is to provide a device.

Another object of the present invention is to control the plasma characteristics by monitoring the plasma characteristics for a long time,
An object of the present invention is to provide a plasma processing method and apparatus capable of maintaining plasma processing characteristics.

Still another object of the present invention is to prevent contamination of a processing wafer due to contamination in the processing chamber by monitoring the contamination state in the processing chamber and to determine an appropriate maintenance (cleaning) time. It is possible to provide a plasma processing method and an apparatus therefor.

Still another object of the present invention is to monitor the processing condition each time one etching process is completed and report the result to the processing device so that the processing device can perform proper processing. It is an object of the present invention to provide an etching monitor capable of maintaining the etching characteristics constant by stopping the processing when the conditions are modified or when the processing conditions cannot be dealt with, thereby preventing the occurrence of defects. .

[0020]

In order to achieve the above-mentioned object of the present invention, in the present invention, the emission of plasma generated in the plasma processing chamber and the emission from a light source outside the plasma processing chamber are performed. Detecting light having a known spectrum that has passed through the inside of the plasma processing chamber, obtaining the difference between the spectra of the plasma emission and the light having the known spectrum, and determining the internal state of the plasma processing chamber from the difference in the spectra. The plasma processing method was used.

Further, in the present invention, a processing chamber having at least a pair of opposing window portions for arranging a wafer to be processed therein and maintaining the processing gas at a predetermined pressure to observe the inside, and the processing gas. Plasma generation means for generating plasma in the processing chamber maintained at a predetermined pressure, plasma emission monitoring means for monitoring plasma emission through one of a pair of opposing window parts outside the processing chamber, and processing. Reference light irradiating means for irradiating the plasma light emission monitoring means with reference light from a side opposite to the plasma light emission monitoring means of a pair of windows outside the chamber, and the plasma light emission monitor. The control means controls the plasma processing state of the wafer to be processed based on the data of the plasma emission and the reference light monitored by the means.

Further, the above object can be achieved by identifying the cause of the change with time of the processing characteristics. Not only the processing characteristics, but also the plasma state changes with time. Therefore, a detailed examination of the change in plasma is considered as follows.

First, the gas is newly released from the film of the reaction product adhering to the inner wall of the processing chamber, whereby the composition of the discharge gas changes, and as a result, the plasma state changes. Further, the film of the reaction product absorbs a part of the supplied discharge power (for example, dielectric loss), so that the power absorbed by the plasma (effective discharge power) changes. Alternatively, in the case of etching a metal wiring film such as aluminum, a thin metal film as a reaction product film adheres to the inner wall of the processing chamber. Will not be absorbed by. In this case also, the effective discharge power changes. The temperature of the inner wall of the processing chamber rises due to the electric discharge, the amount of gas released from the attached film and the amount of secondary electron emitted change, and the plasma state changes.

The change in the plasma state as described above can be observed as a change in the emission spectrum. Therefore, if the characteristics of the change in the emission spectrum due to changes in the discharge power and the characteristics of the changes in the emission spectrum due to changes in the gas composition are obtained in advance and stored in a database, the actual changes in the spectrum can be compared with this database. Thus, the cause of the change in plasma state can be identified. If the cause of the change is something that can be controlled, such as discharge power or pressure,
By correcting this, the plasma can be returned to the original state.

That is, by feeding back the processing conditions (power, pressure, etc.), the plasma can be stably maintained and the processing characteristics can be stabilized. Also, the cause of change is
If it is uncontrollable, such as gas release from the deposits on the inner wall, a warning can be issued and the process can be stopped to prevent the occurrence of defects. Further, this also makes it possible to indicate an appropriate maintenance time.

[0026]

In the window of the etching processing chamber, reaction products are deposited in a film form or the surface of the window is roughened by the impact of ions from the plasma. As a result, when the plasma emission passes through this window, the wavelength component peculiar to the substance forming the adhered matter is absorbed according to the amount, or is diffusely reflected on the inner surface of the window, The amount of light decreases.

In order to quantitatively grasp these situations,
Another light (reference light) is incident from the outside of the processing chamber, passes through the processing chamber, is emitted to the outside of the processing chamber, and is detected by a spectroscope. By comparing the detected reference light with the original spectrum of the reference light (which does not pass through the inside of the processing chamber), the transmittance corresponding to each wavelength can be obtained. Next, turn off the reference light to detect the plasma emission spectrum, and divide by the transmittance obtained using the reference light for each wavelength to correct the detection error due to the effect of the window, and to accurately measure the plasma emission spectrum. You can ask.

On the other hand, the plasma is lost when electrons and ions collide with the inner wall surface of the processing chamber, and the loss is
Replenished by ionization, these are kept in balance. Therefore, when the contact area with the wall surface is large with respect to the volume of plasma, the loss increases and cannot be maintained. As a result, plasma cannot exist, for example, in a cylindrical container that is sufficiently long in diameter. By utilizing this property of plasma, it is possible to prevent contact between the plasma and the window by placing an object having a plurality of elongated holes having a sufficiently small diameter inside the window.

In this case, the light from the plasma can reach the window. However, if this light enters the window while being reflected by the inner wall of the hole, the spectrum of the light will be affected by the reflection. For example, the inner wall will be diffusely reflected by taking a screw shape, and such light (reflected light) will be captured. Keep it out. Further, an inert gas such as Ar is flown through the hole from the window toward the plasma processing chamber so that reaction products in the plasma do not adhere to the window due to diffusion.

By using the above-mentioned plasma emission spectrum correcting means or plasma shielding means,
The emission spectrum of plasma can be measured without being affected by changes with time due to stains on the window, abrasion or the like. This result can be used to monitor the etching properties, as described below.

When plasma is generated and the etching process is started, reaction products of the etching reaction on the wafer surface appear in the plasma and emit light. This emission intensity depends on the supply amount of the reaction product into the plasma, that is, the etching rate, and also on the plasma density. Therefore, the etching rate can be monitored from the emission spectrum. FIG. 5B shows an example of changes over time in the emission intensity of the reaction product.

In the figure, the waveform is composed of four linear components. The emission intensity of the reaction product tungsten (W) corresponds to the emission intensity from the point [A] to the point [B] while the etching is progressing over the entire surface of the wafer, and is almost constant. The emission intensity of W sharply decreases with the end of etching. On the other hand, if the etching rate of W on the wafer surface has a distribution (a fast portion and a slow portion), the area of the etching end portion gradually increases, so that the emission intensity of the reaction product is
It gradually decreases corresponding to the change from the point [B] to the point [C]. At point [D], the plasma discharge in the processing chamber is terminated.
Therefore, the difference in the etching rate of W in the wafer surface, that is, the uniformity can be monitored by the temporal change of the emission intensity of W of the reaction product.

The uniformity of the etching process is defined by the following equation.

[0034]

[Equation 1]

When etching the wiring film, attention is paid to the temporal change of the light emission intensity of the material to be etched (FIG. 5B). Assuming that the end point of etching is t1, the end point of the entire etching is t2, and the film thickness of W is d (nm), the maximum etching rate of the wafer is d / t1 (nm / s) and the minimum etching rate is d / t2. (Nm), average etching rate is 1/2
It becomes x (d / t1 + d / t2) (nm). By substituting these into the above equation, the following equation is obtained.

[0036]

[Equation 2]

Therefore, the uniformity can be calculated from t1 and t2.

FIG. 6A shows an actual waveform. As shown in this figure, in reality, the etching end points of the wafer are non-uniform, so that the fluctuation of the emission intensity becomes large between S1 and point S2, and points of substantially equal curvature are lined up. For this reason,
It is difficult to determine whether to extract S1 or S2 as the extreme value of the second derivative. Therefore, X of the inflection point of the second derivative
It is difficult to extract the coordinate values as t1 and t2.

Therefore, at the point t1 at which the etching is started,
The point t2 at the end of the entire etching surface is extracted by combining the process of smoothing the waveform and then performing the second-order differentiation and the process of approximating the entire waveform by the broken line.

For smoothing processing, an intermediate value filter for removing noise while leaving important information such as edges is used. Figure 6
B shows the result of the second-order differentiation of the actual waveform after the smoothing process and the approximation of the broken line and the actual waveform after the approximation of the broken line. The maximum point when the waveform is second-order differentiated, the point 8 and the point where the etching on the entire wafer surface is completed, and the point 5 coincide. Therefore,
Point 5 is a point at which the entire surface of the etching is completed, and is point 2.

At the start of etching, point 1 has a waveform of 2
It is deviated from point 7 which is the minimum value when the differential is applied. In addition, in each of the constituent points of the polygonal line which is approximated to the polygonal line by point 1, the X coordinate shift is larger than that at the point where the etching is completed. Therefore, the polygonal line is searched from the point 5 in the direction opposite to the change with time, and the starting point of the polygonal line having an inclination equal to or greater than a certain threshold value is set to the point t at which the etching ends.
Set to 1. As a result, it is possible to stably detect the start point of etching and the end point of the entire etching.

The etching uniformity is calculated by substituting the point t1 at the end of etching and the point t2 at the end of the entire etching obtained in the above into (Equation 2).

When the O-ring is exposed to the etching gas and deteriorates, the sealing effect is lost and the air leaks to the inside of the processing chamber. Due to this leak, nitrogen and oxygen that have entered the processing chamber are turned into plasma in the processing chamber and emit light with a specific wavelength. Therefore, regarding the leak, it is possible to detect when the emission intensity is higher than usual by paying attention to the emission wavelength of nitrogen and the emission wavelength of oxygen.

The plasma can be controlled by pressure and plasma generation power, as described below.

When the emission level in the short wavelength region is lower than the standard level, the proportion of electrons having high energy is low. That is, it is considered that the electron temperature is low. Therefore, in this case, the pressure is controlled to be lowered in order to raise the electron temperature. On the contrary, when the level in the long wavelength region is low, the pressure is controlled to be increased. When the level of the entire plasma spectrum is low, it is considered that the emission level is low because the plasma density is low. In this case, the plasma generation power is increased and the plasma density is increased. On the contrary, when the whole level of the plasma spectrum is high, the plasma generation power is reduced to reduce the plasma density.

In addition, the abnormal etching can be monitored by detecting an abnormal light emission peak in the entire waveform.

By the above method, the etching characteristics can be maintained constant by controlling the setting conditions such as pressure and plasma generation power and managing the leak so that the emission spectrum of the plasma does not deviate from the reference value. It will be possible.

Further, as described above, the window of the processing chamber becomes dirty as etching is repeated. This stain is considered to be the same not only in the window but also in other parts of the processing chamber. Therefore, it is possible to estimate the stain inside the processing chamber by monitoring the condition of the stain on the window with the transmission characteristics of the reference light.

FIG. 11 shows the emission spectrum of chlorine plasma when the processing apparatus is new and has never been used.
FIG. 12 shows the spectrum of chlorine plasma similarly in the case of the processing device used for a long period of time. The processing devices are all devices using the microwave ECR method. Although a difference in spectra is recognized by comparing the two figures, the cause of this difference can be estimated as follows.

FIG. 13 shows the spectrum change when only the microwave power is changed in the same processing apparatus. The horizontal axis is the wavelength, and the vertical axis is the spectrum under the central condition divided by the spectrum under each condition, and is expressed in%. 14 and 15 are similar to FIG. 13 when only the pressure and only the chlorine flow rate are changed. If you look at these figures, you can see if there is a change in power or pressure.
It can be seen that the spectrum changes are completely different. That is, from the state of the spectrum change, it is possible to conversely estimate which of the discharge conditions has changed and to what extent. Therefore, controllable conditions (discharge conditions)
If the change in the spectrum due to the change in is previously obtained, the factor of the change in the actual spectrum, that is, the change in the plasma state can be estimated using this as a database.

[0051]

[Example] Quantitatively grasping the state of dirt and scraping of windows,
An example of a method for correcting a spectrum will be described with reference to FIG.

FIG. 1 is an example of an overall view of this apparatus provided with a plasma emission spectrum correction processing means. The configuration of this device will be described.

Reference numeral 2 denotes an etching processing chamber, into which an etching reaction gas is introduced. The gas is controlled by the mass flow controller 9. A parallel plate 22 is provided in the processing chamber 2. Electric power is introduced into the processing chamber 2 by the plasma generating power supply 24. Matching device 23 is used to generate plasma 2
4 and the phase shift of the parallel plate 22 are adjusted. Parallel plate 2
An RF power source 12 for ion control is installed on the lower side of 2. Also, below the parallel plate 22, the wafer thermometer 1
0 is also set. The data from the voltage measuring device 13, the thermometer 10, and the spectroscopic analysis unit 4 enter the data processing control unit 11.

Plasma is generated and the wafer 5 is etched. A lighting window 1 is provided in the processing chamber 2. The light from the reference light source 8 is guided into the processing chamber by the quartz fiber 3 through the lighting window 1. A shutter 6 is provided between the reference light source 8 and the lighting window 1.
To provide. Further, the quartz fiber is used to directly take in the light from the reference light source 8 to the spectroscopic analysis section 4. A shutter 7 is provided between the spectroscopic analysis unit 4 and the reference light source 8.

The operation of this apparatus will be described. Processing room 2
Is evacuated to a vacuum, an etching gas whose flow rate is adjusted by the mass flow controller 9 is introduced, and a predetermined pressure is set. Next, the output of the plasma generating power supply 24 is changed to the parallel plate 2
The upper electrode of No. 2 is applied through the matching unit 23 to generate plasma, and the wafer 5 is etched.

The etching reaction on the surface of the wafer 5 is considered to be a chemical reaction between the active species in the plasma and the material to be etched. By applying a bias voltage with the RF power source 12, ions are attracted to the wafer 5 and the reaction proceeds.

Quartz fibers 3 are attached to the daylighting windows 1 and 1 ', respectively.
In addition, the side of the daylighting window 1 ′ is connected to the reference light source 8 via the shutter 6. Further, the quartz fiber 3 is connected to the spectroscopic analysis section 4 from the reference light source 8 through the shutter 7.

Here, first, the shutter 7 is opened, the reference light of the reference light source 8 is taken into the spectroscopic analysis section 4, and its spectrum is detected. Next, the shutter 7 is closed and the shutter 6 is opened, and the light spectroscopic analysis unit 4 illuminates the reference that has passed through the daylighting windows 1 ′ and 1 to detect the spectrum. In the lighting windows 1 and 1 ', the reaction product generated by the etching treatment adheres to the surface in a film shape, and the sputtering effect of the plasma causes unevenness on the window surface. Although the amount of light diffusely reflected and entering the spectroscopic analysis unit 4 is reduced, and as a result, the transmission characteristics change, the spectrum of the light that is transmitted through the lighting windows 1 and 1 ′ and is collected by the optical spectroscopic analysis unit 4 is changed. , The transmittance of the daylighting windows 1 and 1'corresponding to each wavelength is obtained by correcting the emission intensity of each wavelength with the original spectrum of the reference light that is sampled by the optical spectrum analyzer 4 through the shutter 7. be able to.

Next, the shutter 6 is closed, the reference light source 8 is turned off, and plasma is generated in the processing chamber 2. Processing room 2
The original plasma emission can be obtained by collecting the spectrum of the plasma emission inside the sample through the daylighting window 1 and correcting it with the transmittance of the daylighting window 1 obtained using the reference light. The result of the correction is shown in FIG.

In FIG. 3, [1] is the true value of the plasma spectrum, [2] is the correction value of the plasma spectrum,
[3] is the plasma spectrum that has passed through the daylighting window with changed transmission characteristics.

Next, for the correction of the plasma emission spectrum,
Another embodiment will be described.

FIG. 17 is a block diagram showing an example of a monitor device when the present invention is applied to an etching device. 18 shows an example of a flowchart of monitor signal processing.

In FIG. 17, an etching device 601 is used.
Has a bell jar chamber 600a lighting part 600b. The etching monitor device includes a plasma emission detection unit 6
02, emission signal processing unit 603, etching state monitoring unit 6
04, an output display unit 605. Next, the operation of each unit will be briefly described. Plasma emission detection unit 60
2 obtains the emission spectrum data from the plasma emission 607 of the etching device 601, and sends it to the emission signal processing unit 603 and the etching state monitoring unit 604. Further, the emission signal processing unit 603 corrects the emission spectrum data with the reference emission spectrum data, and sends the corrected emission spectrum data 608 to the etching state monitoring unit 604. The method of this correction will be described later.

The etching state monitoring unit 604 uses the emission spectrum data 608 to estimate the amount and state of reaction products inside the processing chamber of the etching apparatus 601, the deterioration state of parts, and the like, and performs maintenance of the apparatus and etching processing. The information is sent to the output display unit 605 as information such as an abnormal alarm and the data is displayed. Further, setting conditions such as a processing pressure, a gas flow rate, and a power for plasma generation for correcting a deviation from a predetermined etching processing characteristic are obtained, and these are sent to the etching apparatus 601 as feedback signals. Etching device 601
Changes the setting condition by the obtained feedback signal and corrects the deviation from the predetermined etching characteristic.

Next, the correction of the emission spectrum data described above will be described with reference to FIGS. 19A, 19B, 20A, 20B and 20C.

FIGS. 19A and 19B show emission spectra during etching, 201 indicates during etching, and 202 indicates
Indicates that over-etching is in progress. The spectral peaks 211, 212 and 213 change during etching, but hardly change during overetching. The reason for this is that the etching reaction hardly progresses in the over-etching stage. On the other hand, during the etching, a large amount of reaction products are generated and adhere to the inner wall of the bell jar chamber, so that the intensity of the emission spectrum is lowered as a whole.

The deposits increase as the number of processed sheets increases, and the intensity change of the emission spectrum at that time is shown in FIG.
It becomes like 301. That is, the three lines 301 in FIG. 20A show the change in the maximum value of the spectral peaks 211, 212, and 213 in FIGS. 19A and 19B with respect to the number of processed sheets in terms of emission intensity (relative value).

In this figure, the three spectral peaks are
When the number of processed sheets is increased, they all seem to be decreasing. Here, when the emission spectrum of each wafer during over-etching is taken and the intensity of the first wafer is used as a reference and the spectral intensities of the second to fourth wafers are divided, the result is as shown in 302. The numbers 1 to 4 in the figure correspond to the number of processed wafers. Therefore, by correcting the emission intensity of 301 with the wavelength characteristic of 302, it is possible to eliminate the influence of the decrease in the light amount due to the adhesion of the bell jar chamber. In FIG. 20B, 302 is 3
The result of correcting 01 is shown. The spectral peaks 211, 212, and 213, which appeared to be all decreased in 301, are decreased only in 211 as shown in 303, and the other two are not changed.

As described above, the influence of the decrease in the amount of light due to the adhesion of the reaction product on the inner wall of the bell jar chamber can be eliminated by applying the above correction in the signal processing unit of FIG. 17, and stable monitor data can be obtained. it can.

The above description has been made by taking the case of the etching process as an example, but the same can be applied to other processing processes using plasma.

According to the present embodiment, the etching processing state of the wafer in the plasma etching apparatus can be monitored in-process and the processing characteristics can be maintained constant, so that the occurrence of defects can be prevented.

Next, a method for observing the emission spectra of a plurality of specific portions in plasma will be described with reference to FIG. FIG. 16 is a sectional view of an example of the plasma etching apparatus. In FIG. 16, an etching processing chamber 501
Is maintained at a predetermined pressure by a vacuum exhaust system (not shown) and an etching gas introduction mechanism (not shown). Discharge power is supplied to this by a discharge power supply mechanism (not shown), plasma 502 is generated, and the wafer 503 is etched.

The light emission from the plasma is not uniform. For example, the light emission of the etching reaction product is strong at the position 504 near the wafer and adheres to the wall surface at the position 505 near the wall surface of the etching processing chamber 501. The emission gas from the deposit emits light strongly. At the central position 506 of the plasma 502, the emission of the etching gas itself is strong. Therefore, when observing the light emission from the plasma 502, the difference depending on the light emission position can be separated by the lighting optical system provided on the wall surface of the etching processing chamber 501. In FIG. 16, the optical system 507 is focused on the central position 506 of the plasma 502, and only the light emission in this portion is analyzed by the spectroscope 51.
Can be brought to zero. Similarly, the optical system 508 can guide only the light emission in the vicinity 505 of the wall surface of the etching processing chamber 501, and the optical system 509 can guide only the light emission in the vicinity 504 of the wafer 503 to the spectroscope 511 and the spectroscope 512, respectively.

Here, an example of monitoring the etching characteristics of a wafer (W wafer) having a tungsten (W) film formed on its surface will be described.

When the etching process is started, tungsten hexafluoride (W
F ₆ ) is generated and separated into fluorine (F) and W to emit light.
This emission intensity is the amount supplied to the reaction product in the plasma,
That is, it depends on the etching rate and also on the plasma density. Therefore, the etching rate can be monitored from the emission spectrum.

The relationship between the emission intensity of F and the etching rate of the W wafer is shown in FIG. 5A. FIG. 5B is a time-dependent change in the emission intensity of the reaction product W. W which is a reaction product
The light emission intensity of 1 corresponds to the light emission intensity of [A] to [B] while etching is in progress on the entire surface of the wafer, and is substantially constant. With the completion of etching, the emission intensity of W sharply decreases. On the other hand, when there is a difference in the etching rate in the W wafer surface (the fast portion and the slow portion), the area of the etching end portion gradually increases, so the emission intensity of the reaction product changes from [B] to [C]. Corresponding to, gradually decreases.
At [D], plasma discharge in the processing chamber is terminated. Therefore, due to the change with time of the emission intensity of W of the reaction product, W
The difference in etching rate within the wafer surface, that is, the uniformity can be monitored.

The algorithm for uniformity detection is shown in FIG. Further, FIG. 6A shows changes in the emission intensity of plasma during the actual etching process. This is a total of 60 points sampled for 12 seconds at 2 second intervals. Figure 6B
Is a waveform obtained by smoothing the data sampled in FIG. 6A on the basis of the algorithm shown in FIG. 8 to approximate a polygonal line (lines drawn from 1 to 6 in the figure), and smoothing the sampling data. The result of the second-order differentiation by performing the direct polygonal line approximation without performing the above (the line drawn out at 7 and 8 in the figure) is shown.

First, the detected data is subjected to a smoothing process by applying a median value filter of width 3 (extracting the median value from the continuous sampling data of three points). Further, after smoothing the sampling data, a polygonal line approximation is performed, and the polygonal line is viewed in the direction of time change. The starting point of the first polygonal line where the slope is larger than 1 is the etching start point (0
Point) (point 6 in FIG. 6B).

In FIG. 6B, the maximum point when the waveform is second-order differentiated, point 8, and the point where the etching on the entire surface of the wafer is completely finished, point 5 coincide with each other in time. So point 5
Is a point (t2) at which the entire surface of etching is completed. The point at which etching is started, point 1, is deviated from the minimum value, point 7, when the waveform is second-order differentiated. Further, in each of the constituent points of the polygonal line that is approximated to the polygonal line by point 1, the X coordinate shift is larger than that at the end of the entire etching surface. Therefore, a break point is searched from the point 5 in the direction opposite to the time change, and the start point of the etching end point (t) is set as the start point of the broken line having an inclination of a certain threshold value or more.
Detect as 1). As a result, it is possible to stably detect the point (t1) at the start of etching and the point (t2) at the end of the entire etching. By substituting this into the uniformity detection formula (Equation 2), the uniformity can be detected stably.

The etching reaction on the surface of the W wafer is considered to be a chemical reaction between the active species F in the plasma and the material to be etched, but the reaction proceeds when the energy of the F ions incident on the W wafer is supplied. . Also,
The temperature of the W wafer also influences this reaction. Therefore, the etching reaction of the pattern sidewall depends on the temperature of the W wafer and the energy of the ions supplied to the sidewall, and is determined by the bias voltage.

As a result, in FIG. 1, the temperature of the W wafer is measured by the thermometer 10 and the bias voltage is measured by the voltage measuring device 13, and the etching amount of the pattern side wall, that is, the dimensional accuracy can be monitored.

When the O-ring is exposed to the etching gas,
It deteriorates and the sealing performance deteriorates, causing a leak phenomenon in which the atmosphere enters the processing chamber. Nitrogen and oxygen that have entered the processing chamber due to the leak emit light at the position of the emission characteristic of nitrogen and the position of the emission characteristic of oxygen due to the plasma in the processing chamber. Focusing on each of the above wavelengths, the emission intensity is compared with the normal emission intensity, and when the value increases from the normal intensity, it can be detected as a leak.

As described above, the etching characteristics are
It is closely related to the spectrum of plasma emission. Therefore, by keeping the emission spectrum of plasma constant,
The etching characteristics can be kept constant.

The plasma can be controlled by the pressure and the plasma generation power as described below. First, the fact that plasma can be controlled by pressure will be described with reference to FIGS. 7A and 7B. As shown in FIG. 7A, when the emission level in the short wavelength region is lower than the standard level, the proportion of electrons having high energy is low. That is, it is considered that the electron temperature is low. Therefore, in this case, the pressure is controlled to be lowered in order to raise the electron temperature.

On the contrary, as shown in FIG. 7B, when the level in the long wavelength region is low, the pressure is controlled to be increased.
When the whole plasma spectrum level is low, it is considered that the emission level is low because the plasma density is low. In this case, the plasma generation power is increased and the plasma density is increased. On the contrary, when the whole spectrum level is high, the plasma generation power is reduced to decrease the plasma density.

The reaction product of the plasma attached to the daylighting window causes the light passing through the daylighting window to be absorbed at a specific wavelength. Further, the amount of light absorbed at a specific wavelength changes depending on the film thickness attached. Depending on the position where the wavelength is absorbed,
The components of the deposit can be identified and the amount of deposit can be monitored by the amount of absorption in the spectrum. Therefore, it is possible to monitor the stain inside the processing chamber by monitoring the condition of the stain on the window by the change in the transmission characteristic of the daylighting window 1. Data from the thermometer 10 that measures the plasma emission spectrum and the wafer temperature that are collected by the spectroscopic analysis unit 4 and the voltage measurement device 13 that measures the RF power supply 12 are the data processing control unit 11
to go into. The etching characteristic of the wafer 5 is monitored from the calculated value of the data processing control unit 11. In addition, foreign matter can be detected and abnormal etching can be monitored by detecting an abnormal emission peak by looking at the entire waveform.

By the above method, the plasma emission spectrum is prevented from deviating from the reference value of the plasma emission spectrum in the normal etching state. By controlling the settings of the mass flow controller 9 and the RF power supply 12 by the data processing controller 11, the etching characteristics can be maintained constant.

Next, a plasma processing apparatus according to the present invention provided with a plasma shielding means for the daylighting window will be described with reference to FIG.

In the figure, reference numeral 2 denotes an etching processing chamber into which an etching reaction gas is introduced. The gas is controlled by the mass flow controller 9. A parallel plate 22 is provided in the processing chamber 2. Electric power for plasma generation 2
At 4, power is introduced into the processing chamber 2. The matching device 23 adjusts the phase shift between the plasma generating power supply 24 and the parallel plate 22. An RF power source 12 for ion control is installed below the parallel plate 22. A wafer thermometer 10 is provided below the parallel plate 22. Voltage measuring device 13, thermometer 1
0, the data from the spectroscopic analysis unit 4 is the data processing control unit 1
Enter 1.

In such a structure, first, plasma is generated to etch the wafer 5. A lighting window 1 is provided in the processing chamber 2. In the daylighting window 1, the plasma shielding means 1
4 is installed, and light is taken into the spectroscopic analysis section 4 by the quartz fiber 3. A pressure gauge 25 is provided in the processing chamber 2.

The structure of the plasma shielding means 14 attached to the daylighting window 1 in FIG. 2 will be described with reference to FIG. FIG. 4 is a sectional view of the plasma shielding means. This plasma shielding means is attached to the daylighting window 1 of the processing chamber 2 in FIG. In FIG. 4, the wall surface 2 of the processing chamber
0 is provided with a hole 21 of a daylighting window to which a glass plate is not attached, and a shield having a plurality of elongated holes 17 in this portion and the glass plate 15 are attached with an O-ring 16 for vacuum sealing. The left side of the glass plate 15 is atmospheric air, and the right side thereof is a vacuum including the inside of the hole 17. The emitted light of the plasma generated in the processing chamber 1 passes through the glass plate 15 through the hole 17, is condensed by the condenser lens 19, and enters the spectroscopic analysis section 4 through the fiber 3.

Here, the plasma cannot exist in the elongated cylindrical container as described in the section [Operation].

Therefore, if the length of the hole 17 in the axial direction is set to 5 times or more the diameter, electrons are likely to be lost at the inner wall of the hole 17, and plasma cannot enter the hole 17.
As a result, the light from the plasma can reach the glass plate 15, but the plasma does not contact the glass plate 15. Some of the light from the plasma reaches the glass plate while being reflected by the inner wall of the hole 17, but the spectrum of these lights is changing by reflection, so
It needs to be removed. Therefore, if the inner wall of the hole 17 is formed in a screw shape, these lights are attenuated while repeating reflection,
It does not reach the glass plate 15. Furthermore, the gas nozzle 1
Inert gas such as Ar was introduced from 8 and the glass plate 1
By flowing from 5 to the processing chamber through the hole 17, the reaction product does not reach the glass plate 15 by diffusion, and the film does not adhere. As described above, it is possible to prevent the transmission characteristics of the glass plate 15 from changing with time.

For an example of monitoring a W wafer,
This is the same as when the correction processing means is used.

The method of this embodiment can be applied not only to high-frequency discharge plasma but also to direct-current discharge plasma and microwave discharge plasma.

Another embodiment of the present invention will be shown below. FIG.
FIG. 3 is a conceptual diagram of a plasma processing monitor when the present invention is applied to an etching device. Plasma processing monitor
The plasma emission detection 102, the signal detection unit 103, the discharge state estimation unit 104, the data processing unit 105, and the output unit 106. The operation of each unit will be briefly described below. The plasma emission detection unit 102 includes the etching device 10
Emission spectrum data 10 from plasma emission 107
9, the discharge state estimation unit 104 and the data processing unit 1 are obtained.
Send to 05. Further, the signal detection unit 103 receives a signal 108 such as a potential of the substrate to be processed and a set value of process conditions as an input, and a signal 110 processed into a digital signal or the like.
Is sent to the discharge state estimation unit 104 and the data processing unit 105. The discharge state estimation unit 105 estimates the discharge condition using the obtained data, and sends the discharge condition estimation data 111 to the data processing unit 105. The data processing unit 105 uses the discharge condition estimation data 111, the signal 110, and the emission spectrum data 109 to estimate the amount and state of reaction products in the processing chamber of the etching apparatus 101, the deterioration state of parts, and the like, and maintain the apparatus. The data is sent to the output unit 106 and displayed as information (state estimation data 113, alarm output 112) such as an etching abnormality alarm. Further, setting conditions such as a processing pressure, a gas flow rate, and a power for plasma generation for correcting a deviation from a predetermined etching processing characteristic are obtained, and these are used as a feedback signal 114 for the etching apparatus 10.
Send to 1. The etching apparatus 101 changes the setting condition by the obtained feedback signal 114 to correct the deviation from the predetermined etching characteristic.

The main units will be described in detail below.

First, the discharge state estimating section will be described.
Generally, in a plasma processing apparatus, the apparatus deteriorates as the processing is continued, and maintenance work such as cleaning and replacement of parts is required. Due to deterioration of parts, the set process conditions and the effective process conditions in the processing chamber may differ. For example, the flow rate of the processing gas is usually controlled using a device called a mass flow controller so that a predetermined flow rate can be obtained. The mass flow controller is composed of a flow rate measurement unit and a flow rate control unit. Usually, in the flow rate measuring unit of the mass flow controller, the gas flow path is branched into a flow path measuring flow path having a small conductance (flow path 1) and a flow path having a large conductance (flow path 2). The total flow rate can be accurately measured if the conductance ratio of the flow passage 1 and the flow passage 2 does not change. However, for example, if a foreign matter is mixed in one of the flow passages, the conductance ratio of the flow passage 1 and the flow passage 2 changes. , The amount of processing gas different from the predetermined set value is supplied.

In the etching apparatus 101, each item estimated by the discharge state estimating unit 104, the signal 110 and the emission spectrum data 109 are estimated at the same time in advance and stored as a database. By using this, the discharge state is estimated when only the signal 101 and the emission spectrum data are known.

Here, as an example, a case of predicting the power for plasma generation will be described. Etching device 101
Then, the power for plasma generation, the signal 101 and the emission spectrum data 109 are measured. The data obtained is measured a plurality of times for different power levels for plasma generation, and the obtained data is used as a database. If this measurement is repeated a sufficient number of times, each data occupies an area within the signal space. When the number of measurements is small, linearization or an appropriate function is assumed to interpolate between the data, and the area in the signal space is obtained. When the plasma generation power is unknown, only the signal 101 and the emission spectrum data 109 are obtained as known data. A straight line can be obtained by displaying this data in the signal space. The value of the plasma generation power at the point on the straight line where the distance between the point on the straight line and the inner point of the database area is the minimum is the predicted value. Even when there are a plurality of items to be predicted, the predicted value can be obtained by the same procedure.
In addition, as the definition of the distance between two points in the signal space, it is possible to use the sum of squares of differences in coordinate values of each axis, the sum of absolute values of differences, the sum of squares of differences multiplied by a positive weight, or the like. it can.

The data stored as a database can be used to compare a plurality of different devices having the same structure. A database acquired by an etching apparatus (hereinafter referred to as a standard apparatus) serving as a reference for comparison is compared with a database of an etching apparatus to be compared (hereinafter referred to as a comparison apparatus). Generally, the standard device database and the comparator device database occupy different regions in the signal space. The cause of the different areas is considered to be the measurement error and the difference between the standard device and the comparison device. Therefore, parallel movement of each axis to be estimated and conversion of reduction / enlargement are performed to absorb the difference between the databases of the standard device and the comparison device in the signal space. The parameter used at this time, which represents the parallel movement and reduction / enlargement of each axis to be estimated, can quantify the difference between the standard device and the comparison device.

For example, the case where only the power for plasma generation is an estimation target will be described as an example. Compare the database of the standard device and the database of the comparison device. Each point that constitutes the database of the standard device and the comparison device is expressed as a vector.

It is assumed that However, the database plasma generation power of each point W _i: a (i = 1~N). The function for finding the distance is d. At this time

[0104]

(Equation 3)

It is possible to evaluate the degree to which the comparison device is different from the standard device, by obtaining a and b that minimizes. Further, by converting the discharge state estimation data 111 or the signal 110 using the above a and b, the discharge state estimation data of the comparison device can be calibrated with the standard device as a reference. As the definition of the distance, the sum of squares of the difference between the coordinate values of the respective axes, the sum of the absolute values of the differences, the sum of the squares of the differences multiplied by a positive weight, and the like can be used. Further, when there are a plurality of estimation targets, the comparison device can be calibrated with respect to the standard device by the same procedure.

Next, an embodiment relating to the structure of the database will be described. In order to perform arithmetic processing at high speed or in real time, it is desirable that the database is as small as possible. In general, the peaks appearing in the emission spectrum of plasma are not only those that change according to the discharge conditions (plasma generation power, pressure, gas flow rate, etc.) but also those that are unrelated to these changes. As a database, peaks (wavelengths) unrelated to discharge conditions cannot be effectively used. Therefore, by deleting these data from the database, the size of the database can be reduced. The method of distinguishing between valid data and invalid data will be described below.

Here, a method of creating a database of plasma generation power dependency will be described. In order to create this database, the plasma emission spectrum when the plasma generation power is changed is acquired. The emission spectrum is acquired a plurality of times for a certain value of plasma generation power, but the plasma generation power is randomly changed.

That is, the emission spectra are acquired in the order shown in Table 1. In Table 1, the plasma generation power is 9 conditions,
An example is shown in which the number of times of repetition is 10, and the data is acquired 90 times in total. The numbers in the table indicate the order of estimation. The emission spectrum thus measured is arranged as shown in Table 2 for a peak of a certain wavelength.
Therefore, Table 2 is obtained by the number of wavelengths. In Table 2, the vertical columns show the results of repeated measurement with the same plasma generation power, and the horizontal rows show the results corresponding to changes in plasma generation power. In Table 2, the variance for each column (hereinafter, column-wise variance) and the variance for each row (hereafter, row-wise variance) are added. These represent fluctuations due to repeated measurement and fluctuations due to changes in plasma generation power, respectively. If the row-direction dispersion is approximately the same as the column-direction dispersion, it can be said that the emission intensity at this wavelength does not correspond to the amount of plasma generation. Therefore, all the data can be effectively used if the database is configured with only the wavelength at which the row-direction dispersion is sufficiently larger than the column-direction dispersion. Databases for gas flow rate dependency and pressure dependency are created in the same way.

[0109]

[Table 1]

[0110]

[Table 2]

Next, the data processing section will be described. In the data processing unit, the relation between the emission spectrum data 109, the discharge state estimation data 111, and the signal 110 and the event such as the occurrence of a failure of the constituent elements of the etching apparatus 101, the necessity of cleaning is high, the necessity of replacement is high, and the like. It is described in a logical expression and the occurrence of each event in the previous term is predicted from the input data. For example, in the emission spectrum data 109, the emission of 777 nm shows an increase of a predetermined ratio or more as compared with the previous discharge, and the instruction value of the pressure of the processing chamber when the processing gas is not introduced is compared with the previous time. When the increase exceeds a predetermined rate, it is suspected that oxygen was mixed into the processing chamber from the outside, and an alarm output that the leakage has occurred in the processing chamber is issued. Further, when the set value of the gas flow rate and the estimated value of the gas flow rate estimated from the emission spectrum data 109 and the like differ by a predetermined ratio or more, and the exhaust amount of the vacuum pump that exhausts the processing chamber increases, the gas flow rate control mechanism operates. It predicts a failure and gives an alarm. As the logic, binary logic or fuzzy logic can be used.

FIG. 10 shows the hardware configuration of the plasma processing monitor. An optical fiber 205 is connected to a window for acquiring plasma emission of the etching apparatus 201, and plasma emission is made incident on the spectroscope 202. The spectroscope 202 transmits the emission spectrum data to the data processor 203 using the signal line. The etching device 201 and the data processor 203 are also connected by a signal line, and the signal 108 and the feedback signal 114 shown in FIG.
Are exchanged. Output device 2 to data processor 203
04 is connected, and the state estimation data 113 and the alarm output 112 shown in FIG. 1 are transmitted.

Further, another embodiment of the present invention will be described with reference to FIGS. 21 and 22.

FIG. 21 shows a dry etching apparatus according to another embodiment of the present invention.

Generally, in order to detect a device abnormality, it is necessary to define a normal device state and its range. This normal device state will be referred to as a standard state. The standard condition and the current device condition are compared to judge normality / abnormality. FIG. 21 shows an etching apparatus using the present invention. As the device state, (1) microwave reflected power 808 (2) gas flow rate 809 (3) plasma emission spectrum 810 (4) process chamber pressure 811 (5) RF matcher matching state 812 (6) electrostatic chuck voltage , Current 813 (7) RF input / reflected power 814 (8) pressure regulator valve opening 815 (9) wafer temperature 820 (10) coil voltage, current 821 items were converted to digital data by the AD converter 807. After that, the arithmetic processing unit 822 analyzes it to detect a device abnormality. In addition, the arithmetic processing unit 822 can store these device states and take out the device states to the outside when an abnormality is detected or at any time. The past device status can be used for investigating the cause of the abnormality or for device management.

Each item indicating a large number of device states can be recorded for a certain period, and the average value and standard deviation of the device states can be obtained from these data. If the device status is close to the average value, it can be judged to be normal, and if it is far from it, it can be judged to be abnormal. Whether it is close to or far from the average value, that is, the threshold value for abnormality determination can be determined based on the standard deviation. The average value and standard deviation can be obtained from the number of data, the total sum of data, and the sum of squares of data.

As the standard state setting method, (1) the average value and standard deviation obtained in a certain section are used.

(2) The average value and standard deviation are updated each time new data is obtained.

Either one of the two can be used.

As another method for obtaining the normal operating state of the apparatus, the median value and the maximum value in the frequency distribution may be used instead of the average value. Dispersion of operating conditions
Instead of the standard deviation, the variance, the range of the difference between the maximum value and the minimum value, the absolute deviation, or the like can be used.

The procedure for obtaining the standard state of the plasma emission spectrum among the apparatus states will be described below. The time change of plasma emission can be approximated by a line segment for each of a plurality of time regions, and the characteristics of the change can be expressed using the coordinates of the end points of the line segment. The number of regions (how many line segments are approximated) can be determined by the pattern of time change. In the case of the change in the light emission time of the material to be etched during etching, it is appropriate to approximate it with five line segments.

A method of approximating the time change of plasma emission by a plurality of line segments will be described below.

FIG. 22 shows a model of the temporal change in the light emission of the material to be etched. In general, the time change of the light emission of the material to be etched can be divided into five regions as shown in FIG. 22, and the time change can be approximated by approximately five line segments. The algorithm of line segment approximation is shown below.

(1) Maximum and minimum of the second derivative of the emission intensity,
From the start and end of the processing, the initial value (T ₁ 'to T ₆ ') of the time boundary of each area is obtained. However, T _i '<T _{i + 1} ' (i
= 1 to 5), T ₁ ′ is the processing start time, and T ₆ ′ is the processing end time. Further, T ₂ ′ and T ₃ ′ are the maximum and minimum values in the first half, and T ₄ ′ and T ₅ ′ are the minimum and maximum values in the second half, respectively.

(2) Linear approximation is performed by the least square method in the interval (T _i 'to T _{i +1} ').

(3) T _{1 to} T ₆ are obtained from the intersections of straight lines and the start and end times of processing. However, T _i <T _{i + 1} (i = 1 to 1
5), T ₁ (= T ₁ ') is the processing start time, T ₆ (=
T ₆ ') is the end time of the processing. Also, T _{i + 1} is (T _i '
~ T _{i + 1} ') and a straight line (T _{i + 1} ' ~ T
_{i + 2} ') shows the x coordinate of the intersection of the straight lines obtained by the method of least squares. However, i = 1, 2, 3, 4.

[0127] (4) the T ₁ ~T ₆ replace the T ₁ '~T _6'.

(5) It is determined whether or not convergence has occurred, and if not converged, the procedure returns to (2).

The coordinates of the end points of the line segment obtained by the above algorithm represent the characteristic of time change. The end points of each of these line segments will be called feature points. 2 of the above algorithms
The process of obtaining the time at which the maximum and minimum of the differential is obtained may be omitted by using an appropriate initial value. For example, the time of the characteristic point of the time change regarding the substrate processed immediately before can be used as the initial value.

The length of each time region and the emission intensity of each feature point can be obtained from the coordinates of the feature point. With respect to the length of each time region and the emission intensity of each feature point, the average value and standard deviation can be obtained.

Deviations from the linear approximation are processed using the following procedure. For each time domain where the deviation is approximated by a line segment,
It is compressed and decompressed to normalize in time. The average value and standard deviation are calculated for each normalized time.

The change over time of each item indicating the other device state can be expressed by a line segment approximated by the same method and a deviation from the line segment approximation. By performing the data processing for each substrate to be processed, the average value and standard deviation can be obtained. That is, for each measurement item, (1) the average value and standard deviation of the lengths of the time areas approximated by the line segments (2) the average value and the standard deviation of the heights of the feature points (3) the time values approximated by the line segments Obtain the mean and standard deviation of the deviations from the line segment approximation in the region.

The operation algorithm of the abnormality detector is as follows.

(1) Collect the device status.

(2) The apparatus state is modeled by linear approximation.

(3) The standard state and its range are updated.

(4) The present apparatus state and the standard state are compared in consideration of the range of the standard state, and the apparatus abnormality is judged.

(5) If it is determined that the device is abnormal, the process proceeds to (6). When it is determined to be normal, the procedure returns to (1).

(6) The current device status and standard status and their range are output. The extent of the equipment abnormality is judged and the equipment is stopped in the case of a serious abnormality. Issue a minor anomaly report,
Return to (1).

The order of (3) and (4) in the above algorithm may be reversed.

Hereinafter, a method of judging the apparatus abnormality and a method of evaluating the degree of the apparatus abnormality will be described. For each item of device status, a plurality of average values and standard deviations are obtained as described above.
For each average value and standard deviation, a normal range is defined as in equation (1).

[0142]

[Equation 4]

However,

It is

Here, the value of k is determined in consideration of the abnormality detection rate regarding this parameter. It is generally known that when a large number of data are collected, the frequency distribution thereof approaches a normal distribution. It is known that when the parameter is normally distributed, the value of k and the probability of being in the normal range when observing this parameter are as shown in Table 3.

[0146]

[Table 3]

The value of k is determined for each parameter, and it is determined whether the parameter is normal or abnormal. The abnormality content is classified according to which parameter the abnormality has occurred, and how large the deviation from the average value is compared with the standard deviation, and the degree of the apparatus abnormality and the abnormality content are determined.

According to this embodiment, the state of wafer etching processing in the plasma etching apparatus can be constantly monitored and the processing characteristics can be maintained constant.
This is effective in preventing the occurrence of defects.

[0149]

According to the present invention, since the correction means or the plasma shielding means is provided in the daylighting window, it is possible to reduce the influence of the time-dependent change of the light transmission characteristics of the daylighting window due to the influence of the plasma, and the plasma and the etching. The spectrum of the reaction product inside can be stably and accurately monitored. Further, by accurately monitoring the spectrum in such a stable state and controlling the conditions of the etching process, it becomes possible to continue the stable etching process for a long period of time.

Further, according to the present invention, since the etching processing of the wafer of the plasma etching apparatus can be constantly monitored and the processing characteristics thereof can be kept constant, the occurrence of defects can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of the present invention.

FIG. 2 is a block diagram showing the overall configuration of the present invention that employs plasma shielding means.

FIG. 3 is a diagram showing a result of spectrum correction processing.

FIG. 4 is a cross-sectional view showing a shielding means.

5A is a diagram showing the relationship between the emission intensity of tungsten and the etching rate, and FIG. 5B is a diagram showing the change over time of the emission intensity.

FIG. 6 is a diagram showing a temporal change in emission intensity of plasma during an etching process.

FIG. 7 is a diagram showing the relationship between the emission wavelength and emission intensity of plasma.

FIG. 8 is a diagram showing an algorithm for uniformity detection.

FIG. 9 is a conceptual diagram of another embodiment of the present invention.

FIG. 10 is a hardware configuration diagram of another embodiment of the present invention.

FIG. 11 is an emission spectrum diagram in a processing chamber without contamination.

FIG. 12 is an emission spectrum diagram in a dirty processing chamber.

FIG. 13 is a diagram showing a change in emission spectrum due to a change in discharge power.

FIG. 14 is a diagram showing a change in emission spectrum due to a change in discharge pressure.

FIG. 15 is a diagram showing an emission spectrum change according to a change in gas flow rate.

FIG. 16 is a sectional view of the plasma etching apparatus of the present invention.

FIG. 17 is a block diagram of an embodiment of the present invention.

FIG. 18 is a flowchart of signal processing according to the present invention.

19A and 19B are explanatory diagrams of emission spectra.

FIG. 20 is an explanatory diagram of changes in emission intensity.

FIG. 21 shows a configuration of a dry etching apparatus using the present invention.

FIG. 22 shows a time change of light emission of a material to be etched in a dry etching apparatus.

[Explanation of symbols]

1 ... Daylighting window, 2 ... Processing room, 4 ... Spectroscopic analysis unit,
8 ... Reference light source, 11 ... Data processing part, 13 ... Voltage measuring device, 14 ... Shielding means, 507, 508, 509
…Optical system.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H01L 21/205 21/3065 (72) Inventor Toru Otsubo 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Production Engineering Laboratory, Hitachi, Ltd. (72) Inventor Takashi Uemura 5-20-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Stocks, Hitachi, Ltd. Semiconductor Division

Claims (15)

[Claims] 1. In a plasma processing method for plasma processing a substrate, the emission of plasma generated in the plasma processing chamber and a spectrum emitted from a light source outside the plasma processing chamber and passing through the inside of the plasma processing chamber are Plasma processing characterized by detecting a known light, obtaining a difference between respective spectra of the plasma emission and the spectrum known light, and determining the internal state of the plasma processing chamber from the difference between the spectra. Method. 2. A plasma processing method for plasma-treating a substrate, detecting a temporal change in the spectral intensity of an element forming a substrate or a film, smoothing the detected temporal change in the spectral intensity, and then performing a second derivative. When the maximum value of the case is the end point of the entire etching, search in the direction opposite to the time change from the maximum value, and the slope of the polygonal line approximated to the polygonal line is the starting point of the etching end point, which is the specified value or more. A plasma processing method, wherein the uniformity of the plasma processing is detected from the point of completion of the entire surface and the point of start of completion. 3. A processing chamber having at least a pair of opposing window portions for disposing a substrate to be processed therein and maintaining the processing gas at a predetermined pressure to observe the inside, and the processing gas at a predetermined pressure. Plasma generating means for generating plasma in the processing chamber maintained at, and plasma emission monitoring means for monitoring the emission of the plasma through one of the pair of opposing window portions outside the processing chamber; Reference light irradiating means for irradiating the plasma light emission monitoring means with reference light from the opposite side of the plasma emission monitoring means of the pair of opposed window portions outside the chamber through the pair of opposed window portions. A control means for controlling a plasma processing state of the substrate to be processed based on data of the light emission of the plasma monitored by the plasma light emission monitoring means and the reference light. The plasma processing apparatus according to claim. 4. A plasma processing apparatus for plasma-treating a substrate, the processing apparatus comprising: a light source having a known spectrum; a lighting section for extracting plasma emission to the outside; an optical system passing through the lighting section and penetrating the processing chamber; It has an optical system that does not pass through and a spectroscope for performing spectrum analysis, detects the inner surface state of the daylighting section from the difference in the spectrum of the light emitted by the light source obtained by the spectroscope through each optical system, and further detects the inner surface A plasma processing apparatus, wherein an inner surface state of the processing chamber is detected from a state. 5. A plasma processing apparatus for plasma-treating a substrate, a processing chamber for plasma-treating a substrate, a daylighting section provided in the processing room for taking out plasma emission to the outside, and a plasma side of the daylighting section. Plasma having means for shielding plasma, wherein the plasma shielding means is an object provided with a plurality of cylindrical holes whose axial direction is 5 times or more longer than the diameter so that plasma cannot enter. Processing equipment. 6. The plasma processing apparatus according to claim 5, wherein the plasma shielding means has a structure that allows an inert gas to flow from the side of the lighting unit to the side of the plasma. 7. A plasma processing apparatus for performing plasma processing on a substrate, and a processing chamber of the processing apparatus is provided with a lighting section for taking out plasma emission to the outside, a lighting section provided with a plasma shielding means on the plasma side, and each lighting section. A plasma processing apparatus comprising means for detecting an inner surface state of a daylighting section by comparing plasma emission spectra. 8. A plasma processing apparatus for plasma processing a substrate, wherein a processing chamber of the processing apparatus has a daylighting section for taking out plasma emission to the outside, and a processing result of the substrate is obtained from a plasma emission spectrum taken from the daylighting section. A plasma processing apparatus having a detecting function. 9. A plasma processing apparatus for plasma-treating a substrate, wherein a processing chamber of the processing apparatus has a daylighting section for taking out plasma emission to the outside, and the plasma light emission spectrum collected from the daylighting section is constant. A plasma processing apparatus having means for controlling the processing conditions of. 10. A processing chamber having a structure for holding a vacuum, a means for introducing an etching gas into the processing chamber, a means for generating and maintaining plasma in the processing chamber, and an etching processing characteristic of a substrate by observing a plasma state. An etching monitor for a plasma etching apparatus, characterized in that a means for monitoring is provided. 11. An etching monitor of a plasma etching apparatus according to claim 10, wherein a plasma emission spectrum is used as a plasma state monitoring means. 12. An etching monitor of a plasma etching apparatus according to claim 10, wherein an effective value of a processing setting condition is estimated from a monitoring result of a plasma state. 13. A plasma processing apparatus according to claim 10 of the present invention, wherein a difference in processing characteristics between different plasma etching apparatuses is detected from a monitoring result of a plasma state. . 14. A mechanism for measuring an operating state of a plasma processing apparatus, a mechanism for storing the operating state, a mechanism for obtaining a normal operating state and its range from a plurality of the operating states, the normal operating state and a current operation. A mechanism to compare and evaluate states,
A state detection device for a plasma processing apparatus. 15. An average state of the device is obtained by measuring a large number of states and statistically processing the measured data, and comparing the average state and the current state of the device to determine the state of the device. A method for detecting an apparatus state of a plasma processing apparatus to be evaluated.