TW201628086A - Plasma processing apparatus - Google Patents

Abstract

The present invention relates to a plasma processing apparatus aiming to stably detect end point in etching process of small aperture ratio. The solution is characterized in that end point detection can be stably carried out when using high S/N illumination intensity data through obtaining at least two illumination spectrums in etching with weak signal variation to perform end point detection during the etching process of wafers with a small aperture ratio.

Description

Plasma processing device

The present invention relates to a function of detecting an etching end point of a film to be processed which is produced in a semiconductor integrated circuit or the like by using luminescence spectroscopy, in particular, by using an etching process using a plasma discharge, and being provided on a substrate. A plasma processing apparatus that detects the state of processing of a film or the like.

In the manufacture of semiconductor wafers, dry etching is widely used for the removal or patterning of layers of various materials and particularly dielectric materials formed on the surface of the wafer. In the dry etching apparatus, the etching gas introduced into the vacuum processing chamber is plasmatized as an ion or a radical, and when the ion or radical is reacted with the film to be processed on the wafer, the etching is performed. Processing the etching of the film.

In the dry etching process of a semiconductor wafer, the intensity of light emission at a specific wavelength of the plasma light changes as the etching of the film to be processed progresses. Therefore, as a method for detecting an etching end point of a semiconductor wafer, since the dry etching process has been performed, a change in the intensity of the light emitted from a specific wavelength of the plasma is detected, and based on the detection result, the film to be processed is detected. A method of etching the end point that is completely removed by etching.

In the dry etching process of a low aperture ratio wafer having a small exposed area of the material to be etched, the change in the light emission intensity at the end of the etching becomes weak. Further, at the end of the etching, the luminescence intensity of the wavelength of the reaction product generated by etching the material to be etched is reduced.

On the other hand, the luminous intensity at the wavelength of the etching gas (etching agent) is increased. A method of increasing the intensity change at the end of etching by the illuminating intensity of the wavelength of the reaction product and the illuminating intensity of the wavelength of the etchant is known from Patent Document 1 and the like.

In the prior art 1, it is disclosed that in the etching process in which the change in the emission intensity at the end of the etching of the low aperture ratio wafer or the like is weak, the signal indicating the increase in the luminous intensity and the decrease in the luminous intensity at the end of the etching are revealed. Increase weak intensity changes.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2011-9546

However, in the above-described prior art, there are problems in that the following points are insufficiently considered. That is, when a signal having a small intensity level and a large signal are compared, the components of the noise included in the signal of the spectrum of any wavelength or frequency are compared, and the former is relatively variable. Big one. Therefore, at the end of the etching, the difference between the signal intensity at which the luminous intensity is increased and the signal intensity at which the luminous intensity is decreased is remarkably large. For example, in the illuminating or the like in the case of etching a low aperture ratio wafer, the weak illuminance at the end point is displayed. Changes in intensity can have an adverse effect on noise, and it is difficult to detect them correctly.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor crystal which can accurately detect a weak signal intensity change at an etching end point and perform a stable end point detection even when the difference in luminous intensity is large in consideration of the above-described problems of the prior art. Round processing method and processing device.

In the etching process in which the end point detection is performed using a multi-channel spectroscope using a CCD sensor or the like in order to achieve the above object, the difference in signal intensity is large, and the accumulation time for strong signal intensity is created. The illuminance spectrum obtained by setting is set to an illuminance spectrum obtained by setting the accumulation time of the weak signal intensity, and the end point detection is performed at a high S/N using the luminescence spectrum of the plural number.

In the etching using two or more wavelengths of light emission for the end point detection, even if the difference in the luminous intensity is large, the end point detector can be performed with high S/N stability.

1‧‧‧Plastic processing unit

2‧‧‧vacuum processing room

3‧‧‧ Plasma

4‧‧‧Processed material

5‧‧‧Testing table

7‧‧‧ Controller

11‧‧‧Fiber

12‧‧‧ Spectroscope

13‧‧‧Accumulation time setter

14‧‧‧Spectral Replenisher

15‧‧‧wavelength determiner

16‧‧‧Digital Filter

17‧‧‧ Differentiator

18‧‧‧Endpoint determiner

19‧‧‧ Display

601‧‧‧S/N results from the second derivative of the previous method

701‧‧‧S/N results from the 2nd differential value of the present invention

Fig. 1 is a schematic view showing the configuration of a plasma processing apparatus according to an embodiment of the present invention.

Fig. 2 is a view showing the setting of the time of receiving light from the inside of the processing chamber by the embodiment shown in Fig. 1 and the conventional spectroscope.

Figure 3 is a graph showing the spectrum detected using light from inside the processing chamber in the embodiment shown in Figure 1.

Figure 4 is a flow chart showing an outline of a process flow for supplementing the spectrum detected in the embodiment shown in Figure 1.

Fig. 5 is a graph showing an example of a spectrum obtained as a result of the processing shown in Fig. 4.

Fig. 6 is a graph schematically showing optical waveforms of a plurality of wavelengths before and after the end point of the processing obtained in the prior art.

Fig. 7 is a graph schematically showing optical waveforms of a plurality of wavelengths before and after the end point of the processing obtained by the complementary processing of the embodiment shown in Fig. 1.

Embodiments of the present invention will be described below using the drawings.

[Example 1]

Hereinafter, the present invention will be described based on the embodiments shown in Figs. 1 to 7 .

A plasma processing apparatus according to this embodiment is shown in Fig. 1. Fig. 1 is a schematic view showing the configuration of a plasma processing apparatus according to an embodiment of the present invention.

The plasma processing apparatus 1 of the present embodiment includes a vacuum processing chamber 2 disposed inside the vacuum container, and a substrate-like layer placed on the lower side of the vacuum container and placed on the semiconductor wafer or the like in accordance with the mounting process. The sample stage 5 of the material 4 is processed.

The etching gas system introduced into the vacuum processing chamber 2 from the gas introduction means (not shown) is supplied to the processing chamber by an electric field forming means such as a waveguide or a flat or ring-shaped antenna (not shown). The electric field such as a microwave is generated by a magnetic field forming means such as a solenoid coil, and is excited by the magnetic field supplied in the processing chamber, and is separated or decomposed to form the plasma 3. The charged particles formed in the plasma 3 formed in the vacuum processing chamber 2 and the particles having high activity by excitation are provided on the substrate 4 including the semiconductor wafer or the like previously formed on the sample stage 5. The film to be processed by the film structure of the plurality of layers of the photomask is etched.

The light emitted from the particles excited by the plasma 4 is received by a light-receiving member disposed in a vacuum container constituting the vacuum container 2 on the side wall of the vacuum processing chamber 2, and is received by a light receiver disposed outside. The optical fiber 11 is optically connected thereto and introduced into the spectroscope 12. In the spectroscope 12, the light emission of the incident plasma is, for example, in the range of 200 nm to 800 nm, and is split into light wavelengths of a specific interval, and then received light having a light (not shown) of the light of each of the allocated wavelengths. The detector is transformed into a digital signal that shows the intensity of the light at its wavelength.

These signals indicating the light intensity of each of the complex wavelengths are transmitted to the spectral replenisher 14, and the intensity of the spectrum of the complex wavelength is used to supplement the light intensity of the spectrum of the specific wavelength for calculation. A signal indicating the spectral intensity of the complex wavelength including the calculated light intensity of the wavelength is transmitted to the wavelength determiner 15, and the wavelength of the complex number previously detected for the end point determined by the recipe or the like is extracted. In the wavelength determiner 15, a signal output as a sampling signal is stored as a time series data yi in a memory device such as a RAM (not shown).

The time series data yi is smoothed by the digital filter 16, and is stored in the memory device such as the RAM as the smoothed time series data Yi. The smoothing time series data Yi is subjected to calculation of the time series data di of the micro coefficient value (first differential value or second differential value) via the differentiator 17 and stored in a memory device such as a RAM.

Here, the calculation of the micro-coefficient time series data di will be described. As the digital filter circuit 16, for example, a Butterworth type low-pass filter is used twice. The smoothing of the time series data Yi via the second-time Butterworth type low-pass filter is obtained by the equation (1).

Yi=b1. Yi+b2. Yi-1+b3. Yi-2-[a2. Yi-1+a3. Yi-2]...(1)

Here, the coefficients an, bn (n = 1 ~ 3) are based on the number of sampling frequencies and The number of cutoff frequencies, the values are different multipliers. For example, as the present example, when the sampling frequency is 10 Hz and the cutoff frequency is 1 Hz, a2 = -1.143, a3 = 0.4128, b1 = 0.067455, b2 = -0.013491, and b3 = 0.067455.

The time series data di of the second-order micro-coefficient value is in the differentiator 17. For example, the polynomial using the time-series data of five points is suitable for the smoothing-differential method, and is calculated from the following formula (2) as follows.

Here, in the above example, the overlap coefficient wj (j = -2 to 2) is w-2 = 2, w-1 = -1, w0 = -2, w1 = -1, and w2 = 2. Further, in the above example, the calculation of the differentiator 17 uses a polynomial smoothing differential method, but a difference method may also be used.

Whether or not the second-order differential value (or the first-order differential value) obtained by the differentiator 17 satisfies the condition determined in advance by the recipe is judged by the end point determiner 18. When it is determined that the condition is satisfied, the display 7 is displayed on the display 19, and can be connected to the detector and the movable portion provided in the plasma processing apparatus 1 to notify the controller 7 that adjusts the operation of the movable portion. . The controller 7 that has received the communication calculates a command signal necessary for the next processing of the object to be processed 4 or the processing of the object to be processed 4, and transmits the signal to the gas introduction means (not shown) or Microwave power supply, solenoid coil and other plasma forming means.

On a wafer that is etched at a low aperture ratio as the object to be processed 4 In the treatment of the film structure, the change in the luminous intensity from the plasma at the end of the etching is relatively small. Further, depending on the situation, the ratio of the intensity of the noise (SN ratio) is small to the extent that it is difficult to change the detected luminous intensity.

Further, at the end point of the etching, the illuminating intensity at the wavelength of the reaction product generated by etching the film material symmetrically etched on the object 4 is also reduced. On the other hand, the luminous intensity at the wavelength of the etching gas (etching agent) is increased. It is generally known that when the luminous intensity of the wavelength of the reaction product and the luminous intensity of the wavelength of the etchant are removed, the waveform change at the end of the etching can be increased.

Here, the configuration of detecting the end point of the prior art will be described with reference to FIGS. 2, 3, and 6. Fig. 2 is a view showing the setting of the time of receiving light from the inside of the processing chamber by the embodiment shown in Fig. 1 and the conventional spectroscope. Fig. 3 is a graph showing an example of a spectrum detected by using the light from the inside of the processing chamber in the embodiment shown in Fig. 1 and the conventional spectroscope. Fig. 6 is a graph schematically showing optical waveforms of a plurality of wavelengths before and after the end point of the processing obtained in the prior art.

Fig. 2(b) is a diagram showing the setting of the time when the spectroscope of the prior art receives light from the inside of the processing chamber. That is, in the prior art, the period is divided, and in the spectroscope 12, the information on the luminescence obtained by continuously receiving the spectral data of the luminescence is detected, and FIG. 2(b) is schematically displayed in the processed In the processing of the body 4, the processing time varies with the passage of the processing time, and the light-receiving sensor of the spectroscope receives the light-receiving light as one unit (the figure is called "accumulation". The relationship between.

As shown in FIG. 2(b), in the prior art, when the light is continuously received at the same accumulation time B, and the luminescence spectrum is continuously obtained at each accumulation time B, the change in the luminescence spectrum of the plasma is detected. Here, the accumulation time of the multi-channel spectroscope using a CCD sensor or the like will be described.

In the multi-channel beam splitter 12, the photo sensor is charged with a specific wavelength of light that is emitted by the plasma that is split between accumulation times, and accumulates charges inside the sensor or circuit. The charge amount of charge is output after the end of the accumulation time. The amount of charge of each wavelength set as described above is, for example, displayed as an illuminance spectrum as shown in Fig. 3 (a) and Fig. 3 (b) with a wavelength as a parameter. The relationship between the accumulation time and the amount of charge output is approximately proportional. When the accumulation time is doubled, the amount of output charge is also doubled.

An example of the spectrum obtained from the light emission in the etching process of the prior art is shown in FIG. 3(b). The wavelength 1 in Fig. 3(b) is at the end of the etch, and the illuminance is increased, while the wavelength 2 is at the end of the etch, and the luminescence intensity is reduced.

The spectral intensity of the wavelength 1 is as shown in Fig. 6(a), and contains noise, which is only slightly increased at the end of the etching. On the other hand, the spectral intensity of the wavelength 2 is as shown in Fig. 6(b), and contains noise, which is only slightly reduced at the end of the etching.

The left graph of Fig. 6(c) shows the temporal variation of the light intensity at these wavelengths at each time. Convenient, except for the data 6(c), normalized to 30,000 counts. In the right diagram of Fig. 6(c), the second derivative value of the data to be divided is displayed.

In these figures, as indicated by the line of the smoothed arrows, the change in the end point of the etch can be seen as a 10 second generator. When the maximum value of the 2 differentials at the end of such etching is defined as a signal, the signal is 273.9. In addition, the value before 10 seconds can be defined as the amount of noise, and the amount of noise is 170.6. Accordingly, the S/N ratio of the second differential value of the etching treatment was 1.6. These parameters are summarized as shown in Fig. 6(d) and are shown in the table. In general, according to the review by the inventors, the S/N standard of the end point detection can be stably performed at 4.0 or more. According to this standard, in the prior art, such stable end point detection is impossible.

Next, the detection configuration of the end point of the etching process of the present embodiment will be described with reference to Figs. 2(a), 3, 4, 5, and 7.

Although it is repeated, in FIG. 3(b), the spectrum detected from the plasma light emission in the etching process is shown. The wavelength 1 in Fig. 3(b) is at the end of the etch, and the illuminance is increased, while the wavelength 2 is at the end of the etch, and the luminescence intensity is reduced. In addition, the luminous intensity of the wavelength 1 is high, and the wavelength 2 is relatively low. The noise of the circuit in the spectroscope 12 is not dependent on the luminous intensity of the plasma, and the signal detected by the photodetector at the wavelength of the wavelength at which the luminous intensity is low is detected by the photodetector. The department learned that the proportion of noise increased, while S/N was lower.

Therefore, in this example, in order to increase the luminous intensity of the wavelength 2, the accumulation time of different complex values is reversed, and in the spectroscope 12 The intensity of the luminescence is detected. That is, as shown in FIG. 2(a), in the spectroscope 12, the relatively long accumulation time A and the short accumulation time B are alternately repeated, and the light from the processing chamber is received by the photosensor.

The result of detecting the light emission using the light-receiving pattern shown in Fig. 2 (a) is shown in Fig. 3 (a). As shown in Fig. 3(a), it is understood that the spectrum of the detected luminescence is in the wavelength 2, the luminescence intensity is increased, and the S/N system is improved. However, when the period of the accumulation time A becomes longer than a specific value, as shown in the figure, the spectral value of the wavelength 1 is understood to be saturated in the output of the photosensor beyond the limit of the charge that can be accumulated.

Therefore, in the present embodiment, the accumulation time A and the accumulation time B are alternately superimposed, and the light emission is continuously received and detected, and the distribution of the spectral intensity corresponding to each accumulation time is obtained. That is, the distribution data of the spectra shown in each of Figs. 3(a) and (b) are detected.

In the present embodiment, in the spectral replenisher 14, the spectral data of the luminous intensity at different periods obtained in the same processing is detected at a wavelength 1 where the luminous intensity is strong and the luminous intensity is strong. A signal of different intensity values of luminescence in the same process at different wavelengths. Further, a complementary spectrum in which the saturation range of the luminescence spectrum (spectrum A) in which the signal of the intensity of the wavelength 1 is saturated in the accumulation time A is complemented by using these luminescence spectra is calculated.

The calculation algorithm of the supplementary spectrum will be described using FIG. Fig. 4 is a flow chart showing the outline of the processing flow of the spectrum detected in the embodiment shown in Fig. 1.

First, in step 401, after the supplementary processing is started, During the accumulation of time A, the light emitted from the plasma in the processing chamber is received by the photodetector 14 to detect the luminescence spectrum A (step 402). Next, during the accumulation time B following the accumulation time A, the emission spectrum B is detected (step 403).

Next, the range of saturation is detected in the luminescence spectra A, B (step 404). Thereafter, in step 405, the spectral ratios of the two are obtained from the luminescence spectra A, B.

The spectral ratio calculation method uses a ratio of a high peak value of the luminescence intensity of the luminescence spectrum A and B which is not saturated. Alternatively, a ratio of the average value of all or a part of each of the luminous intensities in the range in which the emission spectra A and B are not saturated may be used.

In step 406, comparing the intensity of the luminescence spectral intensity A, B, by adding the saturation range of the intensity-strength spectrum to the spectrum of the low-intensity spectrum, multiplying the value of the spectral ratio obtained at 405, The complementary spectrum shown in Fig. 5 is calculated (steps 407, 408).

In Figure 7, the intensity of the luminescence at the complex wavelengths of the complementary spectrum and the ratios of these are shown. Fig. 7 is a graph schematically showing optical waveforms of a plurality of wavelengths before and after the end point of the processing obtained by the complementary processing of the embodiment shown in Fig. 1. Figure 7 (a) shows the wavelength 1; Figure 7 (b) shows the wavelength 2; Figure 7 (c) shows the temporal change of the intensity of the luminescence of the wavelength 1 / wavelength 2 (left) and its 2 times Time variation of the differential value (right).

In this figure, the second differential value of wavelength 1 (Fig. 7(a) right) is shown, and the second derivative of wavelength 2 (Fig. 7(b) right), Wavelength 1 / Wavelength 2 of 2 differential values (Figure 7 (c) right). In the left and right diagrams of Figure 7(c), the change in the end point of the etch occurs in 10 seconds. When the maximum value of the 2 differentials at the end of the etching is defined as a signal, the signal is 236.2. In addition, the value before 10 seconds can be defined as the amount of noise, and the amount of noise is 45.3. Accordingly, the S/N ratio of the second differential value at the time of this etching was 5.2.

These parameters are summarized and displayed as a table, as shown in Figure 7(d). As described above, the S/N standard of the normal end point detection can be stably performed at 4.0 or more, and the etching system is known to be able to perform the end point detection stably.

In the above embodiment, the spectrum of the light emission is detected in the spectroscope 12, but the present invention is not limited to such a configuration, and the photo sensor of the spectroscope 12 has the amount of charge which is displayed and accumulated during the accumulation time. The signal is applied to the spectral supplement 14 to detect the function of the spectrum before the supplement. In addition, the user of the plasma processing apparatus 1 can arbitrarily set the information of the processing condition (so-called recipe) by using a pointing device such as a computer terminal (not shown). The controller 7 may be configured in accordance with the data of an algorithm or a table set in advance.

As described above, when the end point detection is performed using two or more wavelengths having different illuminating intensities, the illuminating intensity of each wavelength is increased (approximately half or more of the saturated capacity), and each CCD sensor is set. When the time is accumulated, the S/N of the temporal change in the luminous intensity at each wavelength is increased, and when the time is exceeded, the end point detector can be performed at a high S/N. In addition, etching can be performed by calculating the complementary spectrum. The luminescence spectra A, B in the process are collected in one complementary spectrum. Thus, although not shown, it is possible to reduce the memory range of the main memory device such as HD.

1‧‧‧Plastic processing unit

2‧‧‧vacuum processing room

3‧‧‧ Plasma

4‧‧‧Processed material

5‧‧‧Testing table

7‧‧‧ Controller

11‧‧‧Fiber

12‧‧‧ Spectroscope

13‧‧‧Accumulation time setter

14‧‧‧Spectral Replenisher

15‧‧‧wavelength determiner

16‧‧‧Digital Filter

17‧‧‧ Differentiator

18‧‧‧Endpoint determiner

19‧‧‧ Display

Claims (2)

A plasma processing apparatus is a film layer of a processing target to be placed on a wafer in advance, and a film structure having a photomask layer on the film layer, and is disposed in a processing chamber inside the vacuum container, and is formed in the processing described above. A plasma processing apparatus for treating plasma in a room, characterized in that plasma light emission is obtained by a plurality of different light receiving intensities, and the end of the film layer of the wafer is detected using a plurality of wavelengths of the plurality of plasma spectra . The plasma processing apparatus according to claim 1, wherein the spectral range saturated by using the plurality of plasma spectra is used, and the complementary spectrum supplemented by the other plasma spectrum of the unsaturated is used. And detecting the end of the aforementioned film layer of the wafer.