TWI508161B - An etching amount calculating method, a memory medium, and an etching amount calculating means - Google Patents

Description

Etching amount calculation method, memory medium and etching amount calculation device

The present invention relates to an etching amount calculation method, a memory medium, and an etching amount calculation device, and more particularly to an etching amount calculation method when a concave portion such as a groove or a hole is formed on a wafer using a photomask film.

In the manufacturing process of a semiconductor device, etching using a photomask film to form a trench or a hole in an etched layer is performed on a wafer. Although the portion of the etched layer that is not covered by the photomask during etching is physically and chemically removed by the plasma, the depth of the trench must be controlled in the formation of the trench. Therefore, it is necessary to calculate the depth of the trench during etching, that is, the amount of etching, and a method of calculating the conventional etching amount is a method using light interference.

Figure 22 is a diagram for explaining the interference of light in etching.

In FIG. 22, a trench 132 is formed by etching on the wafer W having the photomask film 131 formed on the etched layer 130, but when the wafer W is irradiated with the laser light L1, it is generated. reflected light from the surface of the mask film 131 light L _2, reflected from the mask film 131 is etched and a layer of boundary surface 130 and reflected light L ₃ from the bottom of the trench 132 light L _4.

When the detector receives the reflected light L ₂ to L ₄ , as shown in FIG. 22 , since the optical path length of each reflected light is different only by the thickness of the photomask film 131 or the depth of the trench 132 , the detection is performed. The phase of each of the reflected light of the light receiving surface of the device is different, and interference light (for example, interference light of reflected light L ₂ and reflected light L ₄ (hereinafter referred to as "ditch interference light") or reflected light L ₂ and reflected light L ₃ is generated. Interference light (hereinafter referred to as "mask film interference light").

Then, during the etching, since the depth of the trench 132 changes moment by moment, the optical path length difference between the reflected light L ₂ and the reflected light L ₄ also changes momentarily and the intensity of the interference light changes, that is, the reflected light L ₂ and the reflected light L ₄ generate an interference wave (hereinafter referred to as "ditch interference wave"). Since the period of the interference wave is determined by the rate of change (etching rate) of the depth of the trench 132, the etching rate is calculated from the period of the interference wave, and the etching amount (depth of the trench 132) is calculated from the calculated etching rate and etching time. .

In addition, since the thickness of the mask film 131 is gradually etched and the thickness is changed during the etching, an interference wave (hereinafter referred to as a "mask film interference wave") is generated from the reflected light L ₂ and the reflected light L ₃ . Since each of the interference waves is detected by the same detector, the interference wave detected by the detector is a plurality of interference waves having different periods (hereinafter referred to as "superimposed interference waves") (see FIG. 23).

In order to calculate the depth of the trench 132 (the amount of etching of the layer to be etched 130) from the superimposed interference wave shown in Fig. 23, it is necessary to separate the trench interference wave from the superimposed interference wave.

In the overlapping interference wave of Fig. 23, the short-period interference wave and the long-period interference wave can be relatively clearly separated. Here, since the change speed of the depth of the trench 132 in the etching is greater than the change speed of the thickness of the photomask film 131, the period of the trench interference wave is shorter than the period of the interference film of the photomask film. Therefore, the short-period interference wave in the superimposed interference wave of Fig. 23 is a trench interference wave, and it is possible to easily calculate the period of the trench interference wave from the time between the extreme values in the short-period interference wave ("Δt" in the figure) .

In the method of reading the time between the extreme values of the overlapping interference waves, the short-period interference wave and the long-period interference wave in the overlapping interference wave must be relatively clearly separated, so the short-period interference wave and the long-period interference The overlapping interference wave system in which the wave is difficult to separate cannot calculate the period of the trench interference wave. Further, since the period of the trench interference wave is regarded as constant between the extreme values of the short-period interference waves, the period of the calculated trench interference wave (the etching rate of the layer to be etched 130) is as shown in FIG. It becomes a step. That is, the method of reading the time between the extreme values from the overlapping interference waves has a low decomposition energy.

Therefore, in recent years, there has been developed a method of calculating the period of the trench interference wave by frequency analysis without reading the time between the extreme values of the overlapping interference waves. In this method, a frequency distribution is obtained from a superimposed interference wave by frequency analysis (for example, a fast Fourier transform method) (see FIG. 26(A)), and a period of the trench interference wave is detected from the frequency distribution (for example, refer to Patent Document 1). .

[Patent Document 1] Japanese Patent Laid-Open No. 2-71517

However, as shown in Fig. 25, the overlapping interference wave has an external period due to the abnormality of the laser light source or the detector ("I" in the figure) or the interference between the mask film interference wave and the trench interference wave. Interference such as a change ("II" in the figure) is added to the case where the interference wave is overlapped. In the method of using the frequency analysis described above, since the frequency distribution obtained by the overlapping interference waves passing through all the time in the analysis etching detects only the period of the trench interference wave, when the interference is caused to the overlapping interference wave, the original interference does not exist. Interference cycle When a peak or the like is generated, the frequency distribution is not correct (see Fig. 26(B)), and as a result, the amount of etching cannot be accurately determined.

An object of the present invention is to provide an etching amount calculation method, a memory medium, and an etching amount calculation device which can accurately calculate the etching amount even if interference is given.

In order to achieve the above object, the etching amount calculation method according to the first aspect of the invention is to calculate the etching amount of the concave portion in the substrate etching using the mask film forming concave portion, and the irradiation step is characterized in that the irradiation step is The substrate is irradiated with light; and the light receiving step receives superimposed interference light in which the interference light from the reflected light from the photomask film and the reflected light from the bottom of the concave portion is superimposed on the other interference light; and the interference wave calculating step is performed The superimposed interference light received is used to calculate a superimposed interference wave; the waveform extraction step is to extract a waveform of a predetermined period from the superimposed interference wave; the frequency analysis step is to apply frequency analysis to the extracted waveform; and the interference period detecting step The cycle of detecting an interference wave of the reflected light from the photomask film and the reflected light from the bottom of the concave portion by the frequency distribution obtained by the frequency analysis; and a cumulative averaging step of the predetermined period The interference wave calculation step, the waveform extraction step, and the frequency are repeated only when the predetermined time is shifted a rate analysis step and the interference period detecting step, wherein a cumulative average of the detected interference wave periods is performed for each repetition; and an etching amount etching amount calculation step of calculating the concave portion based on the cumulative average interference wave period The amount of etching.

In the etching amount calculation method according to the first aspect of the invention, the predetermined period is greater than the reflected light from the photomask film and the bottom portion from the concave portion. One period of the waveform of the other interference light having a long period of the interference wave of the reflected light.

The method for calculating an etching amount according to the third aspect of the invention is the method for calculating an etching amount according to the first or second aspect of the patent application, further comprising a pre-analytical processing step of the period of the waveform of the other interference light. When the period of the interference wave from the reflected light from the photomask film and the reflected light from the bottom of the concave portion is longer, the waveform of the predetermined period extracted from the superimposed interference wave is removed from the waveform before the frequency analysis step Most of the portion occupied by the waveform of the interference light, the frequency analysis step applies frequency analysis to a waveform excluding most of the portion occupied by the waveform of the other interference light.

In the etching amount calculation method according to the fourth aspect of the invention, in the pre-analytical processing step, the second polynomial is removed from the extracted waveform. To approximate the waveform of the extracted waveform.

In the etching amount calculation method according to the third aspect or the fourth aspect of the invention, the predetermined period is 1/4 cycle or less of the waveform of the other interference light.

In the etching amount calculation method according to the third aspect of the invention, in the method of calculating the etching amount according to the third aspect of the invention, the opening ratio of the concave portion in the surface of the substrate is 0.5% or less or the concave portion. For deep ditches.

The etching amount calculation method according to the seventh aspect of the invention is the method of calculating the etching amount described in the first or second aspect of the patent application, wherein the frequency analysis system uses a maximum entropy method.

In the etching amount calculation method according to the first or second aspect of the patent application, the method of calculating the etching amount described in the first or second aspect of the patent application has the cycle of the interference wave detected from the frequency distribution. At the time of the abnormal value, the interference period correction step of the period of the interference wave is removed.

In the etching amount calculation method according to the eighth aspect of the invention, in the method of calculating the etching amount according to the eighth aspect of the invention, in the interference period correction step, the value corresponding to the abnormal value is obtained. The period of the interference wave obtained in the predetermined period or the subsequent predetermined period before the predetermined period of the period of the interference wave is regarded as the predetermined period in which the period of the interference wave corresponding to the abnormal value is obtained. The period of the interference wave.

In the etching amount calculation method according to the first or second aspect of the invention, in the etching amount calculation method according to the first or second aspect of the invention, the reflected light from the photomask film and the reflection from the bottom of the concave portion are predicted in advance. In the interference period detecting step, in the frequency distribution obtained by the frequency analysis, the reflected light from the photomask film and the bottom portion from the concave portion are detected from the vicinity of the predicted period The period of the interference wave of the reflected light.

The method for calculating the amount of etching in the 11th article of the patent application is as follows. In the etching amount calculation method according to the first or second aspect, the other interference light is reflected light from the surface of the photomask film, and interference of reflected light from the interface between the photomask film and the substrate surface. Light.

In order to achieve the above object, the memory medium described in claim 12 belongs to a computer-readable memory medium storing a program for causing a computer to perform an etching amount calculation method, and the etching amount calculation method is formed by using a photomask film. The etching amount of the concave portion is calculated in the substrate etching of the concave portion, and the etching amount calculating method includes an irradiation step of irradiating the substrate with light, and a light receiving step of receiving at least the reflected light from the photomask film and The interference light of the reflected light at the bottom of the concave portion is superimposed on the superimposed interference light of the other interference light; the interference wave calculating step calculates the superimposed interference wave from the received superimposed interference light; and the waveform extraction step is performed from the overlapping interference Light extracting a waveform during a predetermined period; a frequency analyzing step of applying a frequency analysis to the extracted waveform; and an interference period detecting step of detecting a reflection from the photomask film from a frequency distribution obtained by the frequency analysis The period of the interference wave of the light and the reflected light from the bottom of the recess; the cumulative average step And repeating the interference wave calculation step, the waveform extraction step, the frequency analysis step, and the interference period detection step while shifting the predetermined period by only a predetermined period of time, and repeating the period of the detected interference wave every time A cumulative average is performed; and an etching amount calculation step of calculating an etching amount of the concave portion based on the cumulative average interference wave.

In order to achieve the above object, the etching amount calculation device described in claim 13 is in the substrate etching in which the concave portion is formed using the photomask film. Calculating an etching amount of the concave portion, comprising: an irradiation portion that irradiates light onto the substrate; and a light receiving portion that receives interference light of at least reflected light from the photomask film and reflected light from a bottom portion of the concave portion The superimposed interference light superimposed on the other interference light; the interference wave calculation unit calculates the superimposed interference wave from the received superimposed interference light; and the waveform extraction unit extracts a waveform of the predetermined period from the superimposed interference light; and the frequency analysis unit The frequency analysis is performed on the extracted waveform; the interference period detecting unit detects the reflected light from the photomask film and the reflected light from the bottom of the concave portion from the frequency distribution obtained by the frequency analysis. a period of the interference wave; the cumulative averaging unit repeats the calculation of the superimposed interference wave, the waveform extraction of the predetermined period, the frequency analysis, and the period detection of the interference wave while shifting the predetermined period by only a predetermined period of time The second iteration is cumulatively averaged over the period of the interference wave detected above; and the etching amount calculation unit is ligated Etching amount of the concave portion of the above-described cumulative average period of the interference wave is calculated.

When the etching amount calculation method described in the first aspect of the patent application, the memory medium described in claim 12, and the etching amount calculation device described in the thirteenth application of the patent application are applied, the predetermined period is only biased. The period in which the overlapping interference wave is calculated, the waveform extraction in the predetermined period, the frequency analysis, and the period of the interference wave from the reflected light from the photomask film and the reflected light from the bottom of the concave portion are repeated for a predetermined period of time, and the repetition is detected every time. Cumulative average of the period of the interference wave, according to the cumulative average The amount of etching of the concave portion is calculated by the period of the interference wave. Therefore, even if, for example, the waveform of a predetermined period of time is disturbed, the period of the interference wave detected based on the waveform of the predetermined period is due to the interference wave detected based on the waveform of the other predetermined period. Since the period is cumulatively averaged, it is possible to reduce the period of the interference wave detected based on the waveform of the predetermined period of the disturbance given, the influence of the period of the cumulative average interference wave, and the correct calculation can be performed even if it is disturbed. the amount.

When the etching amount calculation method described in the second paragraph of the patent application is applied, the predetermined time is longer than other interference light having a longer period than the interference wave from the photomask film and the reflected light from the bottom of the concave portion. Since the one cycle of the waveform is large, the reliability of the frequency analysis of the waveform in the predetermined period can be improved, so that the calculated etching amount can be performed more accurately.

According to the etching amount calculation method described in the third paragraph of the patent application, the period of the waveform of the other interference light is longer than the period of the interference wave of the reflected light from the photomask film and the reflected light from the bottom of the concave portion. At the time of frequency analysis, most of the portion occupied by the waveform of the other interference light is removed by the waveform of the predetermined period extracted from the overlapping interference wave. Therefore, even when the amount of reflected light from the bottom of the concave portion is small, other interference light When the waveform occupies most of the overlapping interference waves, the ratio of the portion of the reflected light from the photomask film and the reflected light from the bottom of the concave portion can be increased in the waveform after the removal, so that in the frequency analysis The period of the interference wave from the reflected light from the photomask film and the reflected light from the bottom of the concave portion can be accurately calculated.

If the etching amount calculation method described in item 4 of the patent application range is applied At the time, the waveform extracted before the frequency analysis is removed, and the waveform of the extracted waveform is approximated by the quadratic polynomial. When the amount of reflected light from the bottom of the concave portion is small, and the waveform of the other interference light occupies most of the overlapping interference wave, since the waveform of the overlapping interference wave and the other interference light are almost equal, the quadratic polynomial is used to approximate The waveform of the extracted overlapping interference wave is also almost equal to the waveform of the other interference light. Therefore, most of the portion occupied by the waveform of the other interference light can be surely removed from the extracted waveform.

According to the etching amount calculation method described in the fifth item of the patent application, the predetermined period is equal to or less than 1/4 of the waveform of the other interference light. Since the waveform of the other interference light that occupies most of the overlapping interference waves is close to the sine wave, if the portion of the waveform of the other interference light is extracted less than or equal to 1/4 cycle, the extracted waveform can be correctly approximated by the quadratic polynomial. Accordingly, most of the portion occupied by the waveform of the other interference light can be correctly removed from the extracted waveform.

When the etching amount calculation method described in the seventh paragraph of the patent application is applied, the maximum entropy method is used for frequency analysis. Therefore, even if the number of waveforms in a predetermined period is small, the reliability of frequency analysis can be improved, so that it can be executed more correctly. Calculation of the amount of etching.

When the etching amount calculation method described in the eighth paragraph of the patent application is applied, since the period of the interference wave detected from the frequency distribution corresponds to the abnormal value, the period of the interference wave is removed, so that the basis can be removed. The period of the interference wave detected by the waveform of the predetermined period of interference is affected by the period of the cumulative average interference wave, and the amount of etching can be calculated more accurately even if it is interfered.

When the etching amount calculation method described in the ninth aspect of the patent application is applied, the predetermined period from the predetermined period of the period of the interference wave corresponding to the abnormal value is obtained or the predetermined period after the predetermined period is obtained. The period of the interference wave is regarded as the period of the interference wave in the predetermined period of the period of the interference wave corresponding to the abnormal value, so that the influence of the interference light detected by the waveform of the predetermined period of the disturbance can be surely removed.

When the etching amount calculation method described in the tenth paragraph of the patent application is applied, the period of the interference wave of the reflected light from the photomask film and the reflected light from the bottom of the concave portion is predicted in advance, and the frequency of the waveform in the predetermined period is used. In the frequency distribution obtained by the analysis, since the period of the interference wave is detected from the vicinity of the predicted period, the detection of the period of the interference wave can be quickly performed, and the value of detecting the abnormality can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, a substrate processing apparatus to which the etching amount calculation method and the etching amount calculation method according to the first embodiment of the present invention are applied will be described. This substrate processing apparatus is configured to etch a semiconductor wafer (hereinafter simply referred to as "wafer") W as a substrate by using plasma. Further, as shown in FIG. 22, the wafer W has an etched layer 130 and a mask film 131 formed on the etched layer 130 in a predetermined pattern.

Fig. 1 is a cross-sectional view schematically showing a configuration of a substrate processing apparatus to which an etching amount calculation method according to the present embodiment is applied.

In FIG. 1, the substrate processing apparatus 10 is provided with, for example, aluminum or the like. The processing chamber 11 made of a conductive material and the bottom surface lower electrode 12 disposed in the processing chamber 11 as a mounting table on which the wafer W is placed are disposed on the lower electrode 12 at predetermined intervals. Above the sprinkler head 13.

An exhaust portion 14 to which a vacuum exhaust device (not shown) is connected is connected to the lower portion of the processing chamber 11, and a high-frequency power source 16 is connected to the lower electrode 12 via the integrator 15, and a buffer chamber 17 inside the shower head 13 is provided. The processing gas introduction pipe 18 is connected, and the processing gas supply device 19 is connected to the processing gas introduction pipe 18. The shower head 13 is a lower portion, and has a plurality of gas pockets 20 that connect the buffer chamber 17, the shower head 13, and the processing space S belonging to the space between the lower electrodes 12. The shower head 13 supplies the processing gas introduced into the buffer chamber 17 from the processing gas introduction pipe 18 to the processing space S via the plurality of gas pockets 20.

In the substrate processing apparatus 10, after the inside of the processing chamber 11 is decompressed to a predetermined degree of vacuum by the exhaust unit 14, the processing gas is supplied from the shower head 13 in a state where the high-frequency voltage is applied from the lower electrode 12 to the processing space S. It is supplied to the processing space S, and plasma is generated from the processing gas in the processing space S. The generated plasma etches the etched layer 130 by the wafer W colliding with the etched layer 130 not covered by the mask film 131, and the trench 132 (concave portion) is formed in the etched layer 130.

The shower head 13 in the processing chamber 11 is provided with a monitoring device 21 that is placed on the lower electrode 12 as viewed from above. The monitoring device 21 is composed of a cylindrical member and penetrates the shower head 13. A window member 22 made of a transparent body such as quartz glass is provided at the upper end of the monitoring device 21. Furthermore, the upper end of the monitoring device 21 and the collecting lens are disposed above the processing chamber 11. 23 and the opposite fiber 24.

The optical fiber 24 is connected to the etching amount calculation device 25 that calculates the etching amount of the layer to be etched 130. The etching amount calculation device 25 includes a laser light source 26 (irradiation portion) and a detector 27 (light receiving portion) that are connected to the optical fiber 24, and a calculation unit 28 (an interference wave calculation unit, a waveform extraction unit, and a waveform extraction unit that are connected to the detector 27). The frequency analysis unit, the interference frequency detection unit, the cumulative average unit, and the etching amount calculation unit operate under the control of the controller 29 of the substrate processing apparatus 10. As the laser light source 26, for example, a semiconductor laser is used. Further, as the detector 27, for example, a photomultiplier or a light-emitting diode is used using the laser light source 27. Further, the controller 29 is connected not only to the calculation unit 28 but also to each component of the substrate processing apparatus 10, for example, the high-frequency power source 16, and controls the operation of each component.

The etching amount calculation device 25 irradiates the laser light from the laser light source 26 toward the wafer W on the lower electrode 12 via the optical fiber 24, the condensing lens 23, and the monitoring device 21, and receives the overlap by the detector 27 via the optical fiber 24 or the like. The reflected light from the wafer W is the overlapping interference light in which the trench interference light (reflected light from the photomask film and the reflected light from the bottom of the concave portion) or the mask film interference light (other interference light) overlaps. . The superimposed interference light received by the detector 27 is converted into an electrical signal and transmitted to the arithmetic unit 28.

The calculation unit 28 calculates the superimposed interference wave from the superimposed interference light based on the received electrical signal. Further, the calculation unit 28 calculates the etching amount of the trench 132 by performing the etching amount calculation method of Fig. 6 which will be described later based on the calculated superimposed interference wave.

Further, the etching rate is not constant during etching, and varies due to various factors (pressure variation of the processing space S or interference of high-frequency voltage). In particular, when etching is formed into a trench having a large aspect ratio (for example, a deep trench), when the etching amount (etching depth) of the trench 132 is increased, the plasma is prevented from entering the trench 132 by having an adhering matter at the entrance of the trench 132. Therefore, the etching rate is lowered (refer to Fig. 2). Further, as shown in Fig. 2, since the etching rate is repeatedly changed slightly, in order to accurately calculate the etching amount of the trench 132, it is necessary to gradually calculate the etching rate.

In order to gradually calculate the etching rate during etching, it is generally necessary to differentiate the waveform of the reflected light from the wafer W at each timing. However, as described above, the reflected light from the wafer W is overlapped trench interference light or light. Since the cover film overlaps the interference light, the etching rate of the trench 132 cannot be accurately obtained even if the waveform of the reflected light is differentiated at each timing.

Here, in the present embodiment, the frequency analysis is performed, and the period of the trench interference wave is calculated from the superimposed interference wave (hereinafter referred to as "ditch interference period"." Further, in the frequency analysis, the waveform of the analysis target is used for one cycle. The above information is long and, in particular, contributes to the improvement of the reliability of the frequency analysis. Therefore, in order to obtain the etching rate at a certain timing, in the present embodiment, the waveform of the predetermined period is extracted from the superimposed interference wave, and the extracted waveform is extracted. Further, as described above, since the etching rate is related to the channel interference frequency, in the present embodiment, the channel interference period is obtained from the extracted waveform, and the etching rate is calculated from the groove interference wave.

FIG. 3 is a view for explaining a waveform extracted from a superimposed interference wave for a predetermined period in the etching amount calculation method according to the present embodiment.

In Fig. 3, since the superimposed interference wave 30 vibrates in a cycle of about 30 seconds, the predetermined period is set to 30 seconds. Here, in order to obtain the groove interference period of the timing A, the waveform of the superimposed interference wave 30 in the period 31 from the timing A to the first 30 seconds (the waveform of the portion surrounded by the square in the figure) is extracted. Further, in the present embodiment, the predetermined period is referred to as a "window". The window 31 has a start point 32 and an end point 33. The start point 32 corresponds to 30 seconds from the timing A, and the end point 33 corresponds to the timing A.

Then, in the present embodiment, the waveform of the extracted window 31 is subjected to frequency analysis. Here, since the waveform extracted is at most one cycle, the maximum entropy method is used as the analysis method. The maximum entropy method is a method of calculating the frequency distribution of observation phenomena with high decomposition energy from the measurement result of extremely short measurement time ("wave data processing for scientific calculation" (CQ Press, issued on April 30, 2011). Since it is not necessary to analyze the number of waveforms of the object, it is more suitable for the etching amount calculation method according to the present embodiment than the fast Fourier transform method which requires a waveform of several cycles.

Fig. 4 is a view showing the frequency distribution obtained from the waveform of the window in Fig. 3 by frequency analysis using the maximum entropy method.

Since the overlapping interference wave 30 mainly contains two of the trench interference wave and the mask film interference wave, the frequency distribution obtained by the waveform of the window 31, as shown in FIG. 4, mainly has two frequencies indicating the peak (interference wave) Period) (about 0.012 Hz and about 0.037 Hz in Fig. 4). Here, as described above, since the period of the trench interference wave is shorter than the period of the interference film of the photomask film (the frequency is high), the frequency of about 0.037 Hz corresponds to the channel interference frequency. Here, the trench interference period detects a frequency of approximately 0.037 Hz. In this way, in the present embodiment, the frequency distribution obtained by the frequency analysis predicts that there are two peaks, and the channel interference period is predicted before the frequency analysis, and the channel interference predicted from the obtained frequency distribution is obtained. The ditches are detected near the cycle.

Since the window 31 includes the waveform of the superimposed interference wave 30 30 seconds from the timing A, the frequency distribution shown in Fig. 4 becomes the frequency distribution in the superimposed interference wave 30 30 seconds from the timing A. Therefore, the groove interference period detected from the frequency distribution shown in Fig. 4 is the average period of the trench interference light in the superimposed interference wave 30 30 seconds from the time series A. However, in the present embodiment, It is convenient to consider the trench interference period detected from the frequency division shown in FIG. 4 as the trench interference period in the timing A. Further, in the present embodiment, as shown later, a plurality of windows are set for the superimposed interference wave 30, and the ditch interference period obtained from the frequency distribution of the waveforms of the respective windows is cumulatively averaged, and the overall average value of the channel interference period is calculated, so that the interference is released. The average period of the trench interference light in the window 31 is regarded as the disadvantage of the trench interference period in the timing A.

Further, in the etching amount calculation method according to the present embodiment, the calculation is performed from the first predetermined period (the start point 32 corresponds to the start of the etching and the end point 33 corresponds to the window 31 30 seconds after the start of the etching). The average value of the etching rates in all the periods until the timing of the etching amount is calculated, and the etching amount is calculated from the average value of the etching rates.

Fig. 5 is a view for explaining a method of calculating the average value of the etching rate in the etching amount calculation method according to the present embodiment, and shows a case where 80 seconds elapse after the start of etching.

In Fig. 5, n windows W _k (k = 1 to n, n is a natural number) shifted by only Δt (predetermined time) are set with respect to the superimposed interference wave 50, and the frequency distribution is obtained in each window W _k From the respective frequency distributions, n trench interference periods f _k (k=1~n, n is a natural number) are detected.

Then, an average of n trench interference periods f _{k is} accumulated according to the following formula (1), The trench interference period f _ave is calculated as the average value of the trench interference waves 80 seconds after the start of etching. Further, when the measurement wavelength (the wavelength of the laser light from the laser light source 26) is λ, the average value of the etching rate is calculated from the following formula (2) to 80 seconds after the start of etching.

The average value of the etching rate = f _ave × λ/2... (2)

Next, the amount of etching from the following formula (3) to 80 seconds after the start of etching was calculated.

Etching amount = average value of etching rate × etching time... (3)

In the etching amount calculation method according to the present embodiment, when the overlapping interference wave 50 in a certain window W _t (t is a natural number of 1 to n) is disturbed, the window W _t The trench interference frequency ft is found to be an abnormal value, but the trench interference period f obtained from the trench interference frequency ft and the other window _Wu (u is a natural number other than 1 to n) _u accumulates the average, so the effect on the interference interval f _ave of the cumulative average trench interference period ft is small.

Next, a method of calculating the etching amount according to this embodiment will be described.

Fig. 6 is a flow chart showing a method of calculating an etching amount according to this embodiment.

In FIG. 6, after the substrate processing apparatus 10 starts etching the etched layer 130 of the wafer W, the laser light source 26 irradiates the laser light L1 toward the wafer W via the optical fiber 24, the condensing lens 23, and the monitoring device 21 (steps). S61) (irradiation step). The detector 27 receives the superimposed interference light belonging to the reflected light from the wafer W via the optical fiber 24 or the like (step S62) (light receiving step).

Next, in step S63, the arithmetic unit 28 determines whether or not the current timing T exceeds the etching end time set in advance, and when the etching end time is exceeded (YES in step S63), the processing is terminated, and when the etching end time is not exceeded ( In step S63, NO), the calculation unit 28 calculates (updates) the superimposed interference wave from the start of etching to the current time T based on the superimposed interference light received by the detector 27 (step S64) (interference wave calculation step) .

Next, the calculation unit 28 extracts the waveform of the window whose end time T is the end point (step S65) (waveform extraction step), and uses the maximum entropy method to The waveform of the extracted window is subjected to frequency analysis (step S66) (frequency analysis step). Here, the time from the start point to the end point of the window is set to be longer than one period of the interference wave of the photomask film.

Thereafter, the calculation unit 28 detects the frequency indicating the peak in the vicinity of the previously predicted trench interference period as the channel interference period in the current time T in the frequency distribution obtained by the frequency analysis (step S67). (Interference cycle detection step).

Next, the arithmetic unit 28 accumulates the channel interference period in the current time T detected by the above-mentioned equation (1), and the timings detected from the time when the first predetermined time elapses until the current time T is reached. In the middle channel interference period (step S68) (cumulative averaging step), the above formula is used according to the measurement wavelength and the etching time (the time from the start of etching to the current time T) from the start of etching to the current time series T ( 2) and (3) Converting the cumulative average trench interference period into the etching amount of the trench 132 (step S69) (etching amount calculation step).

Thereafter, the arithmetic unit 28 updates the current time T by adding Δt to the current time T, that is, shifting the end point of the window by only Δt (step S70), and returns to step S63.

According to the etching amount calculation method according to the present embodiment, the overlapping interference wave, the waveform from the superimposed interference wave extraction window, the frequency analysis, and the detection occurrence timing T are repeatedly calculated while shifting the end point of the window by only Δt. The trench interference period, each repetition, performs a cumulative average of the trench interference period in the detected current timing T and the trench interference period in each of the detected timings from the initial predetermined period to the current timing T. ,will The cumulative average trench interference period is converted into the amount of etching of the trench 132. Therefore, even if, for example, the waveform of the window for a predetermined period of time is disturbed, the channel interference period of the abnormal value obtained from the certain window is cumulatively averaged with the channel interference period obtained from the other window. Therefore, it is possible to reduce the influence of the channel interference period of the trench interference period in which the cumulative average value is abnormal, and it is possible to accurately perform the calculation of the etching amount of the trench 132 even if it is disturbed.

Further, in the etching amount calculation method according to the present embodiment, since the time from the start point to the end point of the window is larger than one cycle of the superimposed interference wave calculated in step S64, the overlapping interference wave in the window can be improved. The reliability of frequency analysis.

Further, in the etching amount calculation method according to the present embodiment, since the maximum entropy method is used for frequency analysis, the reliability of the frequency analysis can be improved even if the number of waveforms of the window is small.

Further, in the etching amount calculation method according to the present embodiment, the trench interference period is predicted in advance, and in the frequency distribution obtained by the frequency analysis, the trench in the occurrence timing T is detected from the vicinity of the predicted trench interference period. Since the interference period is performed, the detection of the channel interference period can be quickly performed, and the value of the abnormality can be detected by suppressing the channel interference period.

Next, a method of calculating the etching amount according to the second embodiment of the present invention will be described.

Since the configuration and operation of the present embodiment are basically the same as those of the above-described first embodiment, the description will be omitted for the repeated configuration and operation, and the different configurations and operations will be described below.

Fig. 7 is a flow chart showing a method of calculating an etching amount according to this embodiment.

In the seventh diagram, steps S61 to S67 are first executed, and then in step S71, it is determined whether or not the channel interference period detected by the calculation unit 28 as the channel interference period in the current timing T corresponds to an abnormal value (for example, in step S67). The maximum frequency or the minimum frequency in the frequency distribution obtained in step S66).

As a result of the determination in step S71, when the channel interference period detected by the channel interference period in the current time T does not correspond to the abnormal value (NO in step S71), the process proceeds directly to step S68, and is detected. When the interference period corresponds to the abnormal value (YES in step S), the trench interference period detected as the trench interference period in the current timing T is removed, and will be one earlier from the corresponding timing T The trench interference period detected by the timing window is set as the channel interference period in the current timing T, and the trench interference period is corrected accordingly (step S72) (interference period correction step).

Next, the arithmetic unit 28 executes steps S68 to S70.

According to the etching amount calculation method according to the present embodiment, when the groove interference period detected as the channel interference period in the current time T corresponds to an abnormal value, the detected groove interference period is removed. And since the trench interference period detected from the window corresponding to the timing T corresponding to the current timing T is set as the channel interference period in the current timing T, the channel interference period pair corresponding to the abnormal value can be removed. The effect of the cumulative average of the trench interference period, and even if it is disturbed The amount of etching of the trench 132 can be calculated more accurately.

In the etching amount calculation method according to the above-described embodiment, when the detected interference period of the trench corresponds to an abnormal value, the trench detected from the window corresponding to the timing T of the comparison timing T is detected. The interference period is set as the channel interference period in the current timing T, but even the trench interference period detected from the window corresponding to the timing of the later timing T is regarded as the trench interference period in the current timing T And it can be set.

Next, a method of calculating an etching amount according to a third embodiment of the present invention will be described.

Since the configuration and operation of the present embodiment are basically the same as those of the first embodiment described above, the point before the waveform is applied to the waveform of the window to be extracted is different, Therefore, the description of the repetitive configuration and the operation will be omitted, and the different configurations and operations will be described below.

When the percentage of the ratio occupied by the opening of the trench 132 in the surface of the wafer W (hereinafter referred to as "opening ratio") is small, for example, less than 0.5%, the reflected light from the bottom of the trench 132 is reflected. _Since the absolute light amount of ₄ is small, the ratio of the portion occupied by the trench interference light in the superimposed interference light received by the detector 27 becomes small.

Fig. 9 is a view showing a change in one of the overlapping interference waves when the aperture ratio is changed.

As shown in Fig. 9, when the aperture ratio is 5%, the overlapping interference waves clearly overlap the two kinds of interference waves (the mask film interference wave and the trench interference wave), but when the aperture ratio is 0.5%, the reflected light The absolute light amount of L ₄ is small, and the waveform of the trench interference wave hardly occurs in the overlapping interference wave. Such a phenomenon is because even when the ratio of the opening portion of the hole is small or the aspect ratio of the trench (or the hole) is large on the surface of the wafer W (for example, when the trench 132 is a deep trench) The absolute amount of reflected light from the bottom of the trench or the hole is also reduced, so that it can occur.

When the waveform of the trench interference wave hardly occurs in the superimposed interference wave (when the aperture ratio is 0.5%), the waveform of the window 31 is extracted from the superimposed interference wave, and when the waveform of the extracted waveform is directly subjected to frequency analysis, Then, in the obtained frequency distribution, the peak of the period of the trench interference wave (the channel interference period) becomes small.

Fig. 10 is a view showing a change in the frequency distribution of the waveform of the time window in which the aperture ratio is changed.

As shown in Fig. 10, when the aperture ratio is 5%, the frequency distribution clearly shows two peaks (the period of the trench interference wave (about 0.8 Hz), the period of the mask film wave (about 0.1 Hz)), but When the aperture ratio is 0.5%, the frequency distribution obviously shows only one peak (the period of the interference film of the photomask film), and the period of the trench interference wave hardly occurs. As a result, the trench interference period cannot be accurately detected, and the etching rate cannot be accurately calculated.

Here, in the present embodiment, most of the portion occupied by the masking film interference wave is removed from the superimposed interference wave before the waveform of the superimposed interference wave extracted by the window 31 is subjected to frequency analysis.

Fig. 11 is a view showing a superimposed interference wave when the aperture ratio is 0.5%.

As shown in Fig. 11, when the aperture ratio is 0.5%, as shown in Fig. 11, since the overlapping interference waves hardly appear as short-distance trench interference waves, the overlapping interference waves are almost interfered by the mask film. Occupied by waves. Therefore, the waveform of the approaching overlapping interference wave is almost equal to the waveform of the interference film of the photomask film. Here, in the present embodiment, the waveform of the superimposed interference wave is removed from the superimposed interference wave. Accordingly, most of the portion occupied by the interference film of the photomask film can be removed from the overlapping interference wave.

Further, as shown in Fig. 11, the overlapping interference wave which is almost occupied by the interference of the photomask film is close to a sine wave, and the portion below the 1/4 cycle of the sine wave can be correctly approximated by the quadratic polynomial. Here, in the present embodiment, when the waveform of the window 31 is extracted from the interference wave, the portion of the photomask film interference wave which is equal to or less than 1/4 cycle is extracted.

In other words, in the present embodiment, as shown in Fig. 12, n windows W _k corresponding to 1/4 cycle or less of the interference film of the photomask film are _{respectively used} (k = 1 to n, n is a natural number) The offset Δt is set, the waveform of each window W _k is extracted, and the waveform of the extracted waveform is extracted by the quadratic polynomial from the extracted waveform, and the waveform occupied by the mask interference film is removed ( Figure 13), and the removed waveform is frequency resolved. Accordingly, as shown in Fig. 14, the frequency distribution in which the peak of the trench interference period (about 0.8 Hz) is apparent can be obtained. Then, the mask film interference wave period (about 0.1Hz) no peak appears in the frequency distribution of FIG. 14, the interference-based film as the mask is removed from the waveform of the window W _k occupies most part of the wave.

Fig. 15 is a view showing an etching amount calculation method according to the present embodiment. Flow chart. Further, the etching amount calculation method according to the present embodiment is performed when the aperture ratio is small, for example, when the aperture ratio is less than 0.5%.

In the fifteenth diagram, the steps S61 to S64 are first executed, and the calculation unit 28 takes the portion of the superimposed interference wave extraction which is equal to or less than the quarter of the end of the current sequence T as the window waveform (step S65) (wave extraction step) ).

Next, the calculation unit 28 calculates a waveform (hereinafter simply referred to as "approximation waveform") of the waveform of the extracted window by the quadratic polynomial (step S151), and removes the calculated approximation from the waveform of the extracted window. The waveform (step S152) (pre-analytical processing step) acquires a waveform in which most of the portion occupied by the interference film of the photomask film is removed, and the waveform obtained by removing the approximating waveform is subjected to frequency analysis (step S153).

Next, the arithmetic unit 28 executes steps S67 to S70.

According to the etching amount calculation method according to the present embodiment, since most of the portion occupied by the mask film interference wave is removed from the waveform of the extracted window before the frequency analysis, even when the aperture ratio is small, for example, the opening is used. When the rate is lower than 0.5%, the waveform after the approximating waveform is removed can also increase the ratio of the portion occupied by the trench interference wave, and thus the frequency distribution of the peak of the channel interference period can be obtained by frequency analysis. As a result, the period of the trench interference wave can be accurately calculated. Further, the etching amount calculation method according to the above-described embodiment can be used only when the period of the waveform of the interference film of the photomask film is longer than the period of the interference light of the trench.

The etching amount calculation method according to this embodiment is a waveform obtained by extracting a window before the frequency analysis, and the second polynomial is used to approximate the waveform. The waveform of the waveform of the extracted window (approximating the waveform). When the aperture ratio is small, the waveform of the superimposed interference wave is almost equal to the interference wave of the photomask film, so that the approximating waveform is almost equal to the mask film. Therefore, most of the portion occupied by the interference film of the photomask film can be surely removed from the waveform of the extracted window.

Further, in the etching amount calculation method according to the present embodiment, a portion of the photomask film interference wave which is equal to or less than 1/4 cycle is extracted as a window waveform. Since the interference film of the photomask film occupying most of the overlapping interference waves is close to the sine wave, if the portion of the interference film of the photomask film is extracted less than 1/4 cycle, the waveform of the extracted window can be correct by the quadratic polynomial. Approaching. Accordingly, most of the portion occupied by the interference film of the photomask film can be removed from the waveform of the extracted window correctly.

Further, when the aperture ratio in the present embodiment is small, not only when the ratio of the opening portion of the surface trench 132 of the wafer W is small, but also to the opening portion of the surface hole of the wafer W. When the ratio is small, or when the aspect ratio of the trench (or hole) is large.

In the above embodiments, the maximum entropy method is used for the frequency analysis, but the fast Fourier transform method may be used even when the number of interference waveforms in each window is large. The high-speed Fourier transform method can calculate the etching amount of the trench 132 more quickly because the number of calculations required by the maximum entropy method is small.

In addition, when the etching amount (etching depth) of a certain trench is calculated using the etching amount calculation method according to each of the above embodiments, when the mask film 131 is a film that transmits laser light, as shown in FIG. Generally, an error occurs between the calculated etching amount ("monitoring depth" in the drawing) and the actually measured etching amount ("etching depth" in the drawing). The interference light that is the superimposed interference light is mainly not the reflected light of the reflected light L ₂ and the reflected light L ₄ , and includes the interference light of the reflected light L ₃ and the reflected light L ₄ , and the optical path length of the reflected light L ₃ changes not only to the photomask film 131 The thickness variation also affects the refractive index of the photomask film 131.

When an error occurs between the calculated etching amount and the actually measured etching amount, the etching amount (etching rate) of the trench 132 is actually measured using the wafer W for the test before the etching amount is calculated, and by the above The etching amount calculation method according to the embodiment is used to calculate the etching amount of the trench 132, and it is preferable to obtain the regression amount of the actually measured etching amount and the calculated etching amount. Then, in the subsequent etching, if the etching amount of the trench 132 is calculated by the etching amount calculation method according to each of the above embodiments, the calculated etching amount may be corrected by regression.

In each of the above embodiments, the etching amount of the trench 132 is calculated. However, even if the etching amount calculation method of FIG. 6, FIG. 7, or FIG. 15 is performed, the etching amount of the hole may be calculated.

Furthermore, the object of the present invention is also to provide a memory medium on which a software code is recorded to a computer (for example, controller 29) for implementing the functions of the above embodiments, and the CPU of the computer reads out And implemented by storing the code stored in the memory medium.

At this time, the program code itself read from the memory medium realizes the functions of the above embodiments, and the memory code constituting the program code and the memory code thereof constitutes the present invention.

Furthermore, as a memory medium for supplying a code, for example, RAM, NV-RAM, floppy disk (registered trademark), hard disk, optical disk, CDs, tapes, non-volatile memory cards, other ROMs, etc., such as CD-ROM, CD-R, CD-RW, DVD (DVD-ROM, DVD-RAM, DVD-RW, DVD+RW) can be memorized The above code can be used. Or the above code can be supplied to a computer even if it is downloaded from another computer or database connected to the Internet, a commercial network, or a regional network.

Furthermore, by executing the program code read by the computer, not only the functions of the above embodiments but also some or all of the actual processing performed by the OS (operating system) running on the CPU according to the instruction of the program code are included. The processing of the above embodiments is realized by the processing thereof.

In addition, the program code read from the memory medium is written into the memory of the function expansion unit inserted into the computer or connected to the computer, and the function is expanded according to the instruction of the code. The CPU or the like provided in the function expansion unit performs part or all of the actual processing, and the processing of the above-described various embodiments is realized by the processing thereof.

The type of the above code may be constituted by a target code, a code executed by a compiler, or a script data supplied to the OS.

[Examples]

Next, an embodiment of the present invention will be described.

Example 1

First, a wafer W composed of an oxide film and a photomask film 131 through which the laser light L1 is transmitted is formed on the etched layer 130 composed of ruthenium, and the etched layer 130 is etched by the substrate processing apparatus 10 by etching. A deep trench 132 is formed. The etching conditions at this time are as follows.

Actual etching rate 1200nm/min

Selecting a ratio of 10 to 1 (the etched layer 130 is applied to the mask film 131)

Opening ratio 0.05

Measuring wavelength (wavelength of laser light L1) 300nm

Sampling rate 10Hz

In the etching of the deep trench 132, the time from the start point to the end point of the window is set to 30 seconds, and the etching amount calculation method of Fig. 6 is performed to obtain the cumulative interference average channel period in each sequence, from which the accumulation is performed. The average trench interference period finds the etch rate of the deep trench 132 in each timing. Then, the obtained etching rate is shown in a graph (refer to Fig. 16).

Comparative example 1

Further, in the etching of the deep trench 132, the detector 27 observes the superimposed interference wave from the wafer W, and reads the short-period interference wave of the superimposed interference wave from the short-period interference wave. The time between the extreme values is determined as the channel interference period, and the etching rate of the deep trench 132 between the extreme values is obtained from the channel interference period. Then, the obtained etching rate is shown in a graph (refer to Fig. 16).

It can be seen from the graph of Fig. 16 that the etching rate of the first embodiment is comparatively comparative. The change in the etching rate of 1 is small and stable.

Further, the error in the etching amount of Example 1 and the error time series in the etching amount of Comparative Example 1 are shown in a graph (see FIG. 17).

As is clear from the graph of Fig. 17, the etching amount of Example 1 was smaller than that of Comparative Example 1. Accordingly, it is understood that the etching amount calculation method of FIG. 6 can accurately calculate the etching amount.

Example 2

Next, a wafer W in which the mask film 131 made of an oxide film is formed on the etched layer 130 made of ruthenium is prepared, and the shallow trench 132 is formed on the etched layer 130 by etching by the substrate processing apparatus 10. The etching conditions at this time are as follows.

Actual etching rate 360nm/min

Selecting a ratio of 10 to 1 (the etched layer 130 is applied to the mask film 131)

Opening ratio 0.2

Measuring wavelength (wavelength of laser light L1) 300nm

Sampling rate 10Hz

In the etching of the shallow trench 132, the time from the start point to the end point of the window was set to 25 seconds, and the etching amount calculation method of Fig. 6 was carried out to calculate the etching amount (etching depth) of the shallow trench 132 in each timing. Then, the calculated etching amount is shown in a graph (refer to Fig. 18).

Comparative example 2

Further, in the etching of the shallow trench 132, the superimposed interference wave from the wafer W is observed by the detector 27, and the frequency distribution is obtained by frequency analysis from all overlapping interference waves from the start of etching to each timing. The trench interference period from the start of etching to each timing is obtained from the frequency distribution, and the etching amount (etching depth) of the shallow trench 132 in each timing is calculated from the trench interference period. That is, the etching amount is calculated from the superimposed interference wave without using the window shown in FIG. Then, the calculated etching amount is shown in a graph (refer to Fig. 18).

In the graph of Fig. 18, the data of the etching amount of Comparative Example 2 is disordered, and the overlapping interference waves are disturbed. In addition, the information on the etching amount of Example 2 is not confusing. Since the second embodiment and the second comparative example are the etching amounts obtained by the interference superimposed interference waves, it is understood that the etching amount calculation method of Fig. 6 can stably calculate the etching amount even if it is disturbed.

Example 3

In the first and second embodiments described above, in the etching of the trenches 132 in the other wafers W, the etching amount calculation method in Fig. 6 is carried out to determine the etching rate of the trenches 132 in the respective timings. Then, the obtained etching rate is shown in a graph (refer to Fig. 19).

Comparative example 3

Furthermore, in the same etching as in Embodiment 3, it is not the maximum entropy method. In addition to the fast Fourier transform method, the etching rate calculation method of the same conditions as the etching amount calculation method of FIG. 6 is performed to obtain the etching rate of the trench 132 in each timing. Then, the obtained etching rate is shown in a graph (refer to Fig. 19).

As is clear from the graph of Fig. 19, the etching rate of Example 3 was smaller than that of Comparative Example 3. Accordingly, it can be understood that the calculation of the etching amount can be performed stably when the maximum entropy method is used.

Example 4

First, a wafer W having an aperture ratio of 5% and a wafer W having an aperture ratio of 0.5% are prepared, and when the etched layer 130 of each wafer W is etched, the etching amount calculation method of FIG. 15 is performed to obtain each etching. rate. Then, the obtained etching rate is shown in a graph (refer to Fig. 20).

Comparative example 4

In the same manner as in the fourth embodiment, a wafer W having an aperture ratio of 5% and a wafer W having an aperture ratio of 05% are prepared, and when the etched layer 130 of each wafer W is etched, the etching amount calculation method of FIG. 6 is performed. Each etching rate was determined. Then, the obtained etching rate is shown in a graph (refer to Fig. 21).

When comparing the graphs of Fig. 20 and Fig. 21, it is understood that when the etching amount calculation method of Fig. 6 is carried out, the etching rate of the opening ratio of 5% is stable, but the etching rate of the aperture ratio of 0.5% is not In the case of performing the etching amount calculation method of Fig. 15, the etching rate of the opening ratio of 5% and the etching rate of the opening ratio of 0.5% are all stable. Accordingly, It can be seen that when the waveform of the window to be extracted is removed from the waveform of the extracted window, the waveform of the extracted window is removed, and the etching rate can be accurately obtained even when the aperture ratio is small.

L1‧‧‧Laser light

L ₂ , L ₃ , L ₄ ‧‧‧ reflected light

W‧‧‧ wafer

10‧‧‧Substrate processing unit

25‧‧‧etching amount calculation device

26‧‧‧Laser light source

27‧‧‧Detector

28‧‧‧ Computing Department

30, 50‧‧‧ overlapping interference waves

31‧‧‧ window

130‧‧‧etched layer

131‧‧‧Photomask

132‧‧‧ Ditch

Fig. 1 is a cross-sectional view schematically showing a configuration of a substrate processing apparatus to which an etching amount calculation method according to the present embodiment is applied.

Fig. 2 is a view for explaining a decrease in etching rate in etching of a trench.

FIG. 3 is a view for explaining a waveform extracted from a superimposed interference wave for a predetermined period in the etching amount calculation method according to the present embodiment.

Fig. 4 is a view showing the frequency distribution obtained from the waveform of the window in Fig. 3 by frequency analysis using the maximum entropy method.

Fig. 5 is a view for explaining a method of calculating an average value of etching rates in the etching amount calculation method according to the present embodiment.

Fig. 6 is a flow chart showing a method of calculating an etching amount according to this embodiment.

Fig. 7 is a flow chart showing a method of calculating an etching amount according to a second embodiment of the present invention.

Fig. 8 is a graph showing the error between the calculated etching amount and the actually measured etching amount.

Fig. 9 is a view showing a change in one of the overlapping interference waves when the aperture ratio is changed.

Fig. 10 is a view showing a change in the frequency distribution of the waveform of the window when the aperture ratio is changed.

Fig. 11 is a view showing a superimposed interference wave when the aperture ratio is 0.5%.

Fig. 12 is a view for explaining the waveform of the extraction window in the etching amount calculation method according to the third embodiment of the present invention.

Fig. 13 is a view showing a waveform of most of the portion occupied by the interference film of the photomask film removed from the superimposed interference wave.

Fig. 14 is a view showing a frequency distribution obtained by frequency analysis of a waveform of a majority of a portion occupied by an interference wave of a photomask film by overlapping interference waves.

Fig. 15 is a flow chart showing a method of calculating an etching amount according to this embodiment.

Fig. 16 is a comparison diagram of the etching rate calculated by the etching amount calculation method of Fig. 6 and the etching rate obtained from the time between the respective extreme values in the interference wave.

Fig. 17 is an error of the etching amount calculated by the etching amount calculation method of Fig. 6 and the actual etching amount, and the etching amount and the actual etching amount obtained from the time between the respective extreme values in the interference wave. A comparison chart of the errors.

Fig. 18 is a comparison diagram of the etching amount calculated by the etching amount calculation method of Fig. 6 and the etching amount obtained by the frequency analysis of the superimposed interference wave from the start of etching to each timing.

Fig. 19 is a comparison diagram of the etching rate calculated by the maximum entropy method and the etching rate calculated by the fast Fourier transform method.

Fig. 20 is a view showing the etching rate of each wafer having different aperture ratios obtained by the etching amount calculation method of Fig. 15.

Fig. 21 is a view showing the etching rate of each wafer having different aperture ratios obtained by the etching amount calculation method of Fig. 6.

Figure 22 is a diagram for explaining the interference of light in etching.

Figure 23 is a diagram showing overlapping interference waves.

Fig. 24 is a view showing an etching rate obtained from the time between the extreme values of the interference wave.

Fig. 25 is a diagram showing overlapping interference waves subjected to interference.

Fig. 26 is a frequency distribution obtained by frequency analysis of overlapping interference waves, Fig. 26(A) shows a case where overlapping interference waves are not interfered, and Fig. 26(B) shows a case where overlapping interference waves are interfered.

Claims (13)

An etching amount calculation method for calculating an etching amount of the concave portion in a substrate etching using a mask film forming concave portion, comprising: an irradiation step of irradiating light to the substrate; and a light receiving step of receiving at least the above The interference light of the reflected light of the mask film and the reflected light from the bottom of the concave portion is superimposed on the superimposed interference light of the other interference light; and the interference wave calculating step calculates the overlapping interference wave from the received superimposed interference light; the waveform is extracted a step of extracting a waveform of a predetermined period from the superimposed interference wave; a frequency analyzing step of applying a frequency analysis to the extracted waveform; and an interference period detecting step of detecting a frequency distribution obtained by the frequency analysis a period of an interference wave from the reflected light of the photomask film and the reflected light from the bottom of the concave portion; and a cumulative averaging step of repeating the interference wave calculation step and the waveform while shifting the predetermined period by only a predetermined period of time Extraction step, frequency analysis step, and interference period detection step described above, each repetition Of the detected period of the interference wave and accumulating the average; and etching amount calculating step, the amount of etching of the recess which lines of an interference wave is calculated from the period of the above-described cumulative average. The method for calculating an etching amount according to the first aspect of the patent application, wherein The predetermined period is greater than one period of the waveform of the other interference light longer than the period of the interference wave from the photomask film and the interference wave from the bottom of the concave portion. The method for calculating an etching amount according to the first or second aspect of the invention, further comprising a pre-analytical processing step of a period of a waveform of the other interference light being higher than a reflected light from the photomask film and from the concave portion When the period of the interference wave of the reflected light at the bottom is long, before the frequency analysis step, the waveform of the predetermined period extracted from the superimposed interference wave is removed from the waveform occupied by the waveform of the other interference light. In the frequency analysis step, frequency analysis is performed on a waveform excluding most of the portion occupied by the waveform of the other interference light. The etching amount calculation method according to the third aspect of the invention, wherein in the pre-analytical processing step, a waveform obtained by approximating the extracted waveform by a quadratic polynomial is removed from the extracted waveform. The method for calculating an etching amount according to the third aspect of the invention, wherein the predetermined period of time is less than or equal to a quarter of a period of a waveform of the other interference light. The method for calculating an etching amount according to the third aspect of the invention, wherein the recessed portion of the surface of the substrate has an aperture ratio of 0.5% or less or the recessed portion is a deep trench. The method for calculating an etching amount according to the first or second aspect of the invention, wherein the frequency analysis system uses a maximum entropy method. The method for calculating an etching amount according to the first or second aspect of the invention, wherein, when the period of the interference wave detected from the frequency distribution corresponds to an abnormal value, the period of the interference wave is removed. Interference cycle correction step. The method of calculating an etching amount according to the eighth aspect of the invention, wherein in the interference period correction step, the predetermined period from the predetermined period of the period of the interference wave corresponding to the abnormal value is obtained. The period of the interference wave obtained in the subsequent predetermined period is regarded as the period of the interference wave in the predetermined period in which the period of the interference wave corresponding to the abnormal value is obtained. The method for calculating an etching amount according to the first or second aspect of the invention, wherein the period of the interference wave from the reflected light of the photomask film and the reflected light from the bottom of the concave portion is predicted in advance, in the interference period detecting step In the frequency distribution obtained by the frequency analysis described above, the period of the interference wave from the reflected light of the photomask film and the reflected light from the bottom of the concave portion is detected from the vicinity of the predicted period. The method for calculating an etching amount according to the first or second aspect of the invention, wherein the other interference light is reflected light from a surface of the photomask film, and reflection from an interface of the photomask film and the surface of the substrate Interference light of light. A memory medium belonging to a computer-readable memory medium storing a program for causing a computer to perform an etching amount calculation method, wherein the etching amount calculation method calculates an etching amount of the concave portion in a substrate etching using a mask film forming concave portion, The etching amount calculation method includes an irradiation step of irradiating light onto the substrate, and a light receiving step of superimposing interference light of at least reflected light from the photomask film and reflected light from a bottom portion of the concave portion a superimposed interference light of interference light; an interference wave calculation step of calculating a superimposed interference wave from the received superimposed interference light; a waveform extraction step of extracting a waveform of a predetermined period from the superimposed interference light; and a frequency analysis step Performing frequency analysis on the extracted waveform; and an interference period detecting step of detecting an interference wave of reflected light from the photomask film and reflected light from a bottom portion of the concave portion from a frequency distribution obtained by the frequency analysis Cycle; cumulative averaging step that shifts the specified period by only a specified time Calculating the interference wave side repeating step, said waveform extracting step, The frequency analysis step and the interference period detecting step perform cumulative averaging on the period of the detected interference wave for each repetition, and an etching amount calculation step of calculating the etching of the concave portion based on the period of the cumulative average interference wave the amount. An etching amount calculation device for calculating an etching amount of the concave portion in a substrate etching using a mask film forming concave portion, comprising: an irradiation portion that irradiates light onto the substrate; and a light receiving portion that receives at least the above The interference light of the reflected light of the mask film and the reflected light from the bottom of the concave portion is superimposed on the interference light by the other interference light, and the interference wave calculating unit calculates the overlapping interference wave from the received superimposed interference light; the waveform extracting unit And extracting a waveform of the predetermined period from the superimposed interference light; the frequency analysis unit applies frequency analysis to the extracted waveform; and the interference period detecting unit detects the frequency distribution obtained by the frequency analysis. a period of an interference wave from the reflected light of the photomask film and the reflected light from the bottom of the concave portion; and a cumulative averaging unit that repeats the calculation of the superimposed interference wave while shifting the predetermined period by a predetermined period of time During the period of waveform extraction, the above frequency analysis and the periodic detection of the interference wave, the above detection is performed for each repetition. The interference wave and accumulating the average period; and an etching amount calculating portion, the amount of etching the recessed portion of which line is calculated based on the interference wave of the cycle of the above-described cumulative average.