JPH10189552A - Terminal detecting method and device of plasma processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to detect the precise terminal regardless of the fluctuation in the plasma state by a method wherein the light emission intensity of the first and second active species is detected to find out the quasi approximate relational expressions of the first active species as well as the ratios and the differential values of both species from these expressions. SOLUTION: Assuming ordinate and abscissa respectively to be the light emission intensity and time, respective experimental expressions are found out by the method for least squares using the first and second wave forms 1, 2 of the light emission intensities within the mean times. Next, the quasi approximate linear relational expression A' of the first active species is found out from the approximate linear relational expression A of the first active species and the approximate linear relational expression of the second active species. Furthermore, the differential value d (A/A')/dt of the ratio A/A' is detected. The waveforms for A/A' are respectively stabilized in a specific forms before and after terminals. Finally, the terminals can be decided precisely by detecting the starting of change (slope start: S.S) and the ending of change (slope end: S.E) without fail.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for detecting an end point of a plasma process.

[0002]

2. Description of the Related Art Conventionally, a plasma processing apparatus, particularly an etching apparatus, has been widely applied to a semiconductor manufacturing process or a manufacturing process of a substrate for a liquid crystal display device. Such an etching apparatus includes, for example, an upper electrode and a lower electrode disposed in parallel with each other, and generates plasma from an etching gas by a discharge between the upper electrode and the lower electrode, and generates an active species of the plasma. Then, a film of a semiconductor wafer having a film such as an oxide film formed thereon as an object to be processed is etched. In such an etching process, it is desired to monitor the progress of the etching and detect the end point as accurately as possible to perform the etching process according to a predetermined pattern.

Conventionally, as a method of detecting the end point of etching, instrumental analysis techniques such as mass spectrometry and spectroscopic analysis have been used, and among them, relatively simple and highly sensitive spectroscopic analysis is widely used. . When spectroscopic analysis is used to detect the end point of etching, specifically, a specific type of active species such as an etching gas, radicals such as decomposition products or reaction products, or active species such as ions is used. The species is selected, and the change of the luminescence intensity of the selected active species with respect to time is measured. In this case, the active species to be selected differs depending on the type of the etching gas and the material to be etched. For example, when a silicon oxide film is etched using a fluorocarbon-based etching gas such as CF ₄ , CO ^* , which is a reaction product thereof and whose emission intensity sharply decreases at the end point, is used. In this case, the emission intensity with respect to time from CO ^* (219 nm or 483.5)
nm) (only one wavelength is used),
A method of determining the end point of etching by comparing the amount of change in the emission intensity and the primary differential value and the secondary differential value of the intensity with respect to time, as disclosed in Japanese Patent Application Laid-Open No. 63-81929. ^{* The} emission intensity with respect to the time from ^* and the reference light of two wavelengths (in JP-A-63-81929, the emission spectrum intensity of atoms such as helium is 706.
A method of measuring the light emission intensity with respect to time of 5 nm and 667.8 nm) and comparing the respective light emission intensity ratios or the amount of change of the first derivative, the second derivative, etc. of the ratio, to determine the end point of etching. Similarly, as a method using two wavelengths, as disclosed in JP-A-5-29276 (corresponding U.S. Pat. No. 5,322,590), the emission intensity with respect to time from CO ^* and the above-described reference light Instead of CF ^* , which is a decomposition product of an etching gas whose emission intensity rises sharply at the end point, with respect to time, and measures the ratio of each emission intensity or the first derivative and second derivative of the ratio. There is known a method of determining the end point of etching by comparing the amount of change with respect to time.

In a conventional endpoint detection method using one wavelength,
The end point of the plasma processing becomes unclear due to the fluctuation of the light emission intensity due to the fluctuation of the plasma, and the end point cannot be detected accurately. In the conventional endpoint detection method using two wavelengths, the end point time of the emission intensity of CO ^* , which is the active species of the reaction product, and the emission intensity of CF ^* , which is a reference light or a decomposition product of etching gas whose emission intensity sharply increases at the end point, CF ^* The light emission intensity ratio between the two is simply taken into account, without taking into account that the amount of change with respect to the plasma fluctuation, the temperature change of the chamber, electrodes and wafer, and the deposits attached to the chamber walls, etc.
Since the end point is detected using the ratio, it is also difficult to accurately detect the end point.

[0005] US Pat. At 5,565,114, when the present inventors use two wavelengths to detect the end point of etching using the emission intensity ratio at each wavelength, the inventors agree on the amount of change with respect to time for both emission intensities. The idea of taking the ratio between the two (that is, making the slopes of the change curves of the light emission intensity with respect to time coincide) is disclosed. Certainly, rather than simply monitoring the ratio of the two, as disclosed in this publication (US Pat. No. 5,565,114), the slopes of the change curves of the two are matched beforehand. By monitoring the ratio, the end point can be detected more accurately.

[0006]

However, according to the method disclosed in this US patent, the two slopes are made to coincide with each other by calculating the average value of the change curve of the light emission intensity in the designated section before the end point, and calculating the average value in the designated section. Since the sum of the absolute values of the difference between the light emission intensity and the average value is obtained for each of the change curves, and the sum is used (that is, the area is calculated), there is a disadvantage that it is weak to noise. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for detecting an end point of a plasma process which can accurately detect an end point while allowing a change in a plasma state.

[0007]

According to a first aspect of the present invention, there is provided a method for detecting an end point of a plasma process, comprising the steps of: Detecting the luminescence intensity of each of the first and second active species having a specific wavelength, and outputting the luminescence detection information; and, based on the luminescence detection information, determining the relationship between the luminescence intensity and time. Obtaining the approximate relational expression A of the first active species and the approximate relational expression B of the second active species, and using the approximate relational expression A of the first active species and the approximate relational expression B of the second active species. Obtaining a pseudo-approximate relational expression A ′ of the first active species, the approximate relational expression A of the first active species and the pseudo-approximate relational expression A ′ of the first active species
From the ratio (A / A ') and the differential value (d
(A / A ′) / dt), the ratio (A / A ′) within the designated period, and the derivative of the ratio (d (A /
A ′) / dt), and the ratio (A / A ′) is plotted on the horizontal axis, and the differential value (d (A / A ′) / dt) of the ratio is plotted vertically. On the axis, the graph having the origin at the intersection of the average value of the ratio (A / A ') and the average value of the differential value of the ratio (d (A / A') / dt) within the designated period, A predetermined value of the ratio (A / A ') calculated from the information of the dispersion tendency and a differential value of the ratio (d (A
/ A ′) / dt) to set a predetermined area from a predetermined value, and a ratio (A / A ′) using emission detection information of the first and second active species during processing after the specified period. And the derivative of the ratio (d (A / A ') / dt) are determined, and the ratio (A / A') and the derivative of the ratio (d (A / A '
Determining the time when the position in the graph of ') / dt) deviates from the predetermined area as the end point of the plasma processing.

According to another aspect of the present invention, there is provided a method for detecting an end point of a plasma process, wherein when performing a process using a plasma on an object to be processed, a first period and a second period after the specified period during the plasma process. The step of sequentially detecting the light emission intensity at a specific wavelength of light emission from the active species by light detection means and outputting light emission detection information, and the relationship between the light emission intensity and time based on the light emission detection information within the designated period. Obtaining the approximate relational expression A of the first active species and the approximate relational expression B of the second active species in the step of; and the approximate relational expression A of the first active species and the approximate relational expression B of the second active species Calculating a pseudo-approximate relational expression A ′ of the first active species using the following equation; and, from the approximate relational expression A of the first active species and the pseudo-approximate relational expression A ′ of the first active species, Ratio (A / A ′) and the derivative of the ratio (d (A / A ′) / Dt), and a step of calculating the average value and dispersion tendency of the ratio (A / A ') and the differential value of the ratio (d (A / A') / dt) within the designated period. , The ratio (A / A ′) is plotted on the horizontal axis, the differential value of the ratio (d (A / A ′) / dt) is plotted on the vertical axis, and the average of the ratio (A / A ′) within the designated period is taken. A graph having the origin at the intersection of the value and the average value of the differential value of the ratio (d (A / A ') / dt) shows the emission of the first and second active species during the processing after the designated period. The ratio (A / A ′) obtained by using the detection information and the derivative of the ratio (d
(A / A ') / dt) when the position in the graph deviates from the origin and approaches the horizontal axis again as a finish point of the plasma processing. Still another method of detecting the end point of the plasma processing according to the present invention is that, during the processing using the plasma on the object to be processed, the emission intensity at a specific wavelength of each of the first and second active species generated by the plasma, Detecting during and after a designated period during processing, and outputting the light emission detection information;
Based on the light emission detection information, an approximate relational expression A of the first active species and an approximate relational expression B of the second active species that represent a straight line or a curve by approximating the change in the emission intensity with the passage of time.
And substituting the elapsed time of the approximation relational expression B of the second active species into the elapsed time of the approximation relational expression A of the first active species to obtain a pseudo approximated relational expression A ′ of the first active species From the approximate relational expression A of the first active species and the pseudo approximated relational expression A ′ of the first active species, the ratio (A / A
′) And the derivative of the ratio (d (A / A ′) / dt), and the ratio (A / A ′) and the derivative of the ratio (d (A / A ′) within the designated period. ) / Dt), and the ratio (A / A ′) is taken on one axis of the rectangular coordinate system, and the differential value (d (A / A) of the ratio is taken on the other axis. ') / Dt), and the intersection of the average value of the ratio (A / A') and the differential value of the ratio (d (A / A ') / dt) within the designated period is defined as the origin. A prepared graph is prepared, and a predetermined value of the ratio (A / A ′) calculated from the information of the dispersion tendency and a predetermined value of the differential value (d (A / A ′) / dt) of the ratio are prepared. Setting a region, and using the light emission detection information of the first and second active species during the processing after the designated period, the ratio (A / A ′) and the ratio Minute value (d (A / A ') / d
t) is determined, and when the position of the determined ratio (A / A ′) and the derivative of the ratio (d (A / A ′) / dt) in the graph deviates from the predetermined region, the plasma processing end point is determined. And a step of determining.

The step of obtaining the approximate relational expression A of the first active species and the approximate relational expression B of the second active species comprises the step of calculating the approximate linear relation A of the first active species and the approximation of the second active species. The step of obtaining a linear relational expression B, wherein the step of obtaining the pseudo-approximation relational expression A ′ of the first active species is performed by the step of obtaining an approximate linear relational expression A of the first active species and an approximate primary relation of the second active species. Using a relational expression B, a pseudo approximate linear relational expression A of the first active species
The step of calculating the ratio (A / A ′) and the differential value of the ratio (d (A / A ′) / dt) includes:
From the approximate linear relation A of the first active species and the pseudo approximate linear relation A ′ of the first active species, the ratio (A /
A ′) and the differential value of the ratio (d (A / A ′) / dt)
Is desirable.

[0010] The end point detection apparatus for plasma processing according to the present invention comprises:
Light detecting means for detecting a change in emission intensity at a specific wavelength of the first and second active species with respect to time, which is generated by the plasma when performing processing using the plasma on the object to be processed, and performing emission detection information; An approximate relational expression A of the first active species and an approximate relational expression B of the second active species are obtained based on the emission detection information within the designated period, in relation to the emission intensity and the time,
Using the approximate relational expression A of the first active species and the approximate relational expression B of the second active species, a pseudo approximate relational expression A ′ of the first active species is obtained, and an approximation of the first active species is obtained. From the relational expression A and the pseudo-approximation relational expression A ′ of the first active species, a ratio (A / A ′) of the two and a differential value of the ratio (d (A / A ′))
/ Dt), and calculates the ratio (A / A ') within the designated period.
Calculating means for calculating the average value and dispersion tendency of the differential value (d (A / A ') / dt) of the ratio, and the ratio (A / A') on the horizontal axis, and calculating the differential value of the ratio ( d (A
/ A ′) / dt) is plotted on the vertical axis, and the intersection of the average value of the ratio (A / A ′) and the differential value of the ratio (d (A / A ′) / dt) is defined as the origin. Graphing means for creating a graph, and the ratio (A / A) calculated from the information on the dispersion tendency.
') And the derivative of the ratio (d (A / A') /
dt), a predetermined area is set from a predetermined value, and the ratio (A / A ′) and the differential value of the ratio (d) are determined using the emission detection information of the first and second active species during the processing after the specified period.
(A / A ') / dt), and the ratio (A / A)
') And a determination means for determining when the position of the differential value of the ratio (d (A / A') / dt) in the graph deviates from the predetermined area as the end point of the plasma processing. I do.

As the first active species and the second active species,
It is desirable to use an active species whose emission intensity becomes weaker and an active species which becomes stronger at the end point of the plasma processing after the designated period.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method and an apparatus for detecting an end point of a plasma process according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. During the plasma processing, the plasma state is unstable because it is affected by various conditions such as applied power, gas flow rate, pressure, and plasma temperature (plasma fluctuations). Therefore, the emission intensity of the active species used for detecting the end point of the plasma processing is also unstable.

The fluctuation of the light emission intensity has two components: a periodic or single noise fluctuation as shown in FIG. 1 and a drift fluctuation which gradually increases or decreases with time as shown in FIG. 1 and 2, the vertical axis represents the light emission intensity, and the horizontal axis represents time. It is known that the noise fluctuation is mainly caused by a slight change in the high frequency power, the gas flow rate, and the pressure, and the drift fluctuation is mainly caused by a time fluctuation of the plasma temperature.

As disclosed in JP-A-63-81929 and JP-A-5-29276, the noise fluctuation is 2
By using the wavelength, the common fluctuation component can be canceled out by obtaining the intensity ratio of both wavelengths, and it can be basically removed. However, when the ratio between the emission from the active species and the reference light or another active species is simply taken and the ratios are compared, when the drift (the overall slope of the waveform) is different,
The fluctuation component cannot be sufficiently removed.

The present inventors diligently studied the above points and found that US Pat. As disclosed in US Pat. No. 5,565,114, drift variation is removed and accurate end point detection is performed by comparing the amount of change with the differential value of the light emission intensity of light having a wavelength temporally adjusted. I found that I can do it. However, U.S. Pat. The method disclosed in US Pat. No. 5,565,114 for temporally adjusting the differential values of the emission intensities of the two wavelengths of light (that is, matching the slopes of the emission intensity change curves of the two wavelengths) is the background of the invention. As described above, since the area calculation is used, there is a disadvantage that it is susceptible to noise. In view of the above, the present inventors have further improved the method of matching the slopes of the emission intensity change curves of the two wavelengths, and have therefore improved the accuracy of end point detection.

Next, the end point detecting method of the present invention will be specifically described. First, when performing a process using plasma on the object to be processed, a specified period (averaging time) during the plasma process.
First, each having a specific wavelength (for example, a peak wavelength)
And the emission intensity of the second active species is sequentially detected by the light detection means. Next, based on the luminescence detection information of the first and second active species within the averaging time (that is, a change in luminescence intensity with respect to time), the approximate primary of the first active species in the relationship between luminescence intensity and time A relational expression A and an approximate linear relational expression B of the second active species are obtained respectively. That is, as shown in FIG. 3 in which the vertical axis represents light emission intensity and the horizontal axis represents time, the change waveforms 1 and 2 of the light emission intensity of the first active species within the averaging time
From the least squares method using the emission intensity waveform 2 of
Find the empirical formula for each. In this case, approximate linear relational expressions A and B (Expression 1 and Expression 2) are obtained as experimental expressions.

Y ₁ = a ₁ × X + b ₁ (A) Equation 1 Y ₂ = a ₂ × X + b ₂ (B) Equation 2 (where Y ₁ and Y ₂ are the first and second activities, respectively) X represents the elapsed time, and a ₁ , a ₂
Represents a linear coefficient, and b ₁ and b ₂ are Y intercepts (Y-int
Next, a pseudo approximate linear relation A ′ of the first active species is obtained from the approximate linear relation A of the first active species and the approximate linear relation B of the second active species. That is, X in Equation 1 is replaced by Equation 2
Is substituted to obtain a pseudo-approximation linear relational expression A ′ (Equation 3).

Y ₁ = (a ₁ / a ₂ ) × (Y ₂ −b ₂ ) + b ₁ (A ′) Equation 3 Both Equations (1) and (3) are the light emission amounts of the first active species. Y ₁ and the ratio (A / A ′) (FIG. 3)
Inside, a curve indicated by reference numeral 3 is obtained for reference. Further, the differential value (d (A / A ') / d of this ratio (A / A')
Find t). Note that this ratio (A / A ′) becomes substantially 1 when the two active species show the same tendency (characteristic) of a change in emission intensity, and becomes larger or smaller as the tendency becomes different. That is, when the two active species show different tendencies, as shown in FIG. 3, the value of this ratio is determined before the end point (before a slope start: SS described later).
And constant at the end point, large change (increase or decrease) at the end point
Then, after the end point (after a slope end: SE described later), it becomes constant again. Here, the term “end point” is used for convenience, but this does not refer to an instant but refers to a certain period (time from SS to SE), as shown in FIG. It can be understood from the description that follows.

Next, the end point is determined based on the results shown above. As described above, the waveform for the ratio (A / A ′) stabilizes constantly before the end point and after the end point (does not change over time). Therefore, by setting a threshold value between these two fixed values (before the end point and after the end point), the end point can be easily detected by the threshold value detection. However, in detecting such an end point, the ratio (A
If the threshold is set at a position very close to the beginning or end of the change in the waveform of / A '), the end point may not be detected stably. For this, the threshold is
S. S. And S. E. FIG. It is desirable to set a period slightly away from both.

In the present invention, the start of the change (slope start: SS) and the end of the change (slope end: SE) are detected with high accuracy as described below to accurately determine the end point. be able to.

The ratio of the emission intensities (A
/ A ') and its derivative, that is, the slope (d (A / A
FIG. 4 shows the time change of ') / dt). As can be seen from FIG. 4, the ratio (A / A ′) is constant before the end point, greatly decreases at the end point, and becomes constant again after the end point. The slope (d (A / A ') / dt) is constant before the end point, shows a peak that greatly decreases at the end point, and becomes constant after the end point in the same manner as before the end point.

The luminous intensity ratio (A / A ') is plotted on the horizontal axis,
The derivative of the ratio (d (A / A ') / dt) is plotted on the vertical axis, and the average of the ratio (A / A') and the derivative of the ratio (d (A / A ') /
When the values are plotted on a graph of two-dimensional coordinates having the origin at the intersection with the average value of dt), the result is as shown in FIG. As can be seen from FIG. 5 which shows the passage of time as a curve, before the end point,
It is distributed in the center of the coordinates, and when the change starts near the end point,
The coordinates largely jump to the first quadrant or the third quadrant (the third quadrant in FIG. 5). After the end point, it approaches the horizontal axis and is distributed near this. In this way, by expressing on the two-dimensional coordinates, the relationship between the ratio (A / A ′) and the differential value of the ratio (d (A / A ′) / dt) and the state change of the waveform for each can be visualized. For example, a program can be processed and viewed as an image.

In determining the end point, first, the ratio (A / A ') within the averaging time and the differential value of the ratio (d (A / A'))
/ Dt) and the average value and the tendency of dispersion are determined.
The averaging time is set in a period before the end point of the plasma processing. The starting point of the averaging time is preferably set not at the start of the plasma processing but at the time when the plasma is stabilized.

Next, an initial fluctuation range (predetermined value) in the graph is calculated from a predetermined value, which will be described later, calculated from information on the dispersion tendency of the ratio (A / A ') and the differential value of the ratio (d (A / A') / dt). Area). This fluctuation range (predetermined area)
As shown in FIG. 6, a predetermined value of the ratio (A / A ') calculated from information on the dispersion tendency in the specified period (averaging time) and a predetermined value of the differential value of the ratio (d (A / A') / dt) It is preferably set by the square root r ₁ of the sum of squares with the value. Actually, the ratio (A / A ′) calculated from the dispersion tendency information and the differential value of the ratio (d (A / A ′) / dt) ) Is calculated as the square root of the sum of squares of the predetermined value {[(predetermined value of ratio) ² + (predetermined value of slope (differential value of ratio)) ² ]} (C) This is a circular range indicated by a dotted line P, which is the origin O. Therefore, before the end point, a large amount is distributed within the circle P, and when the change near the end point starts, the circle gradually moves away from the circle P. Here, the maximum value of the difference between the ratio and the average value of the ratio is used as the predetermined value of the ratio (A / A ′) calculated from the information of the dispersion tendency,
As the predetermined value of the differential value of the ratio (d (A / A ') / dt), the maximum value of the difference between the differential value of the ratio and the average value of the differential values of the ratio can be used.

Based on the above fact, a time when the variation range is exceeded is determined as a slope start. However,
Since the slope start cannot be accurately determined near the fluctuation range, for example, a position (value) for determining the end point outside the fluctuation range on the graph is set, and the distance L1 from the position to the origin and the fluctuation range are set. The slope start is determined by comparing with the radius L2 of the circle. That is,
A ratio (A / A ′) and a differential value of the ratio (d (A / A ′) / dt) are obtained using the emission detection information of the first and second active species during the processing after the averaging time, and are graphed. The distance L1 from the upper position to the origin is obtained, and this distance is compared with the radius L2 of the fluctuation range obtained from the light emission detection information within the averaging time.

Specifically, the ratio (A / A ') corresponding to the position for determining the end point and the differential value of the ratio (d (A / A') /
dt) and the square root of the sum of the squares of the differences between the respective average values (origins) {[(ratio−average value of ratio) ² + (slope−average value of slope) ² ]} (D) The point where the ratio (D / C) to the square root of the sum of squares (C) becomes larger than a preset threshold value is determined as a slope start.

On the other hand, the slope end is the differential value of the ratio (d
(A / A ') / dt), that is, determination is made based on the inclination approaching the horizontal axis again (approaching the variation range of the inclination). That is, the slope for determining the end point is compared with a predetermined value obtained from the variance tendency, and the result is obtained from ((slope−
Average value of slope / predetermined value) is obtained, and a point where this value becomes smaller than a preset threshold value is determined as a slope end. Note that the predetermined value obtained from the dispersion tendency is calculated as described above.

When the slope end is used for end point detection, the ratio (A / A ') obtained by using the emission detection information of the first and second active species during the processing after the designated period.
When the position in the graph of the differential value of the ratio (d (A / A ') / dt) deviates from the origin and approaches the horizontal axis again, it is determined as the end point of the plasma processing.

In this case, similarly to the case where the slope start is used for detecting the end point, a fluctuation range is set, and the ratio and the ratio are determined by using the emission detection information of the first and second active species during the processing after the designated period. The differential value of the ratio may be obtained, and the time when the position of the obtained ratio and the differential value of the ratio in the graph falls within the fluctuation range (predetermined region) may be determined as another end point of the plasma processing. The setting of the fluctuation range is similar to the case where the slope start is used for detecting the end point.

In the case where the slope end is used for detecting the end point, similarly to the case where the slope start is used for detecting the end point, a new origin and a variation range may be sequentially set, and the end point may be detected a plurality of times. .

As described above, in the determination of the end point, the direct comparison with the threshold value is not performed, and the predetermined value obtained from the information within the averaging time of the plasma processing is used for the determination of the end point. Drift fluctuation which cannot be removed by the conventional end point detection method can be sufficiently removed. Therefore, even if the S / N (signal noise) is bad, the end point can be accurately detected. Note that the actual plasma processing end point may be the slope start position or the slope end position. This selection is appropriately performed depending on the purpose and conditions of the plasma processing.

In the end point detection method of the present invention, as shown in FIG. 7A, even when the waveform of the temporal change of the ratio of the light emission intensity has a shape rising near the end point, as shown in FIG. )
As shown in the above, the slope start and the slope end can be determined in the same manner as described above. In this case,
It can be seen that the resulting curve greatly jumps out into the first quadrant of the coordinates.

When holes are formed by etching two different types of films, for example, as shown in FIG. 8, a SiO ₂ film 5 and a Si ₃ N ₄ film 6 are sequentially formed on a silicon substrate 4. In the case of etching, FIG.
As shown in the figure, the waveform of the time change of the ratio of the light emission intensity rises in the first time, that is, near the end point of the first stage, and rises in the second time, that is, in the second time,
The shape is lowered near the end point of the second stage. In this case, as shown in FIG. 9B, after the first end point is detected as described above, the obtained ratio (A / A ′) and the derivative of the ratio (d (A / A The point where the position in the graph of A ′) / dt) intersects the horizontal axis of the graph again is defined as a new origin O _2.
From the predetermined value of the ratio (A / A ′) calculated from the information of the dispersion tendency and the predetermined value of the differential value (d (A / A ′) / dt) of the ratio, another predetermined region (variation range) R ₂ Set the first
And the ratio (A / A) using the emission detection information of the second active species.
') And the derivative of the ratio (d (A / A') / dt), and the ratio (A / A ') and the derivative of the ratio (d
(A / A') / position in the graph of dt) is determined as the second endpoint of the plasma treatment when deviating from the other predetermined areas R ₂ (slope start). In FIG. 9B, O ₁ is the origin at the time of the first end point detection,
R ₁ is a fluctuation range at the time of the first end point detection. Also,
The determination method of the second slope start and slope end is performed in the same manner as described above.

As a result, the final point of etching for forming a hole in the Si ₃ N ₄ film 6 and the subsequent SiO ₂
The end point of the etching for forming a hole in the film 5 can be recognized. Technology, as shown in FIG. 10, the aspect on the SiO ₂ film 5 in which the substrate 7 on the portions to thick formed there is a step different repeating determination of such origin movement performed slope start and the slope end The present invention can be applied to the case where holes 8a to 8c having different ratios are formed. Also in this case, as shown in FIGS. 11A and 11B, by performing the origin movement in the same manner as described above, it is possible to determine the slope start and slope end a plurality of times, The end point of the etching process of each step can be accurately detected. In addition,
In FIG. 11B, O ₁ is the first time, ie, the origin at the time of detecting the end point of the first stage, O ₂ is the second time, ie, the origin at the time of detecting the end point of the stage, and O ₃ is the third time. That is, the origin at the time of detecting the end point of the third stage is respectively shown, R ₁ is a fluctuation range at the time of the first end point detection, R ₂ is a fluctuation range at the time of the second end point detection, R ₃
Indicates a fluctuation range at the time of the third end point detection.

Next, an embodiment performed to clarify the effect of the method for detecting the end point of the plasma processing of the present invention will be described. FIG. 12 is a diagram schematically showing the configuration of a plasma processing apparatus provided with an end point detection apparatus according to the present invention, for example, a plasma etching apparatus. The plasma processing apparatus 10 includes:
Processing chamber 11 made of a conductive material such as aluminum
And a lower electrode 12 disposed in the processing chamber 11 and serving also as a mounting table for mounting the semiconductor wafer W as an object to be processed.
And an upper electrode 13 disposed above the lower electrode 12 so as to be separated from the lower electrode 12, and a plasma generation region is defined between these electrodes.

A gas introduction pipe 14 for introducing a processing gas, for example, a fluorocarbon-based etching gas such as CF ₄ is connected to an upper portion of the processing chamber 11. An exhaust pipe 15 for discharging generated gas is connected to a side wall of the processing chamber 11. The lower electrode 12 is grounded and is always kept at the ground potential. Also, the upper electrode 13
Is connected to a high-frequency power supply 16, and by applying a high-frequency voltage from the high-frequency power supply 16 to discharge between the lower electrode 12 and the upper electrode 13, the etching gas is activated to generate radical species, ionic species, and the like. Plasma P composed of active species is generated in a plasma generation region.

A monitoring window 17 made of a transparent material such as quartz glass is attached to the side wall of the processing chamber 11. The emission spectrum of the plasma P is transmitted through the window 17 and the transmitted light is analyzed. Monitor the progress of the etching. A lens 21 for condensing transmitted light is provided outside the window 17, and further behind the lens 21,
A photodetector 22 that detects light collected by the lens 21 and performs photoelectric conversion is provided. This photodetector 22
Is composed of, for example, a pair of interference filters or spectrometers, and a pair of photomultipliers or photodiodes. The light of two specific wavelengths is separated by the interference filter or spectroscope, respectively, and then separated. The light of each wavelength is photoelectrically converted, and transmitted as an electric signal indicating a change in light emission intensity with respect to time. Based on two electric signals corresponding to a change in emission intensity with respect to time transmitted from the photodetector 22, an end point of the etching is detected by the arithmetic unit 30, which will be described later, and a control signal is sent to the control unit 40 when the end point is detected. To the plasma processing apparatus 10 via the control device 40.
, That is, the transmission of the high-frequency power supply 16 is stopped to end the etching.

Here, the position of the lens 21 can be appropriately moved in the vertical direction by lens moving means (not shown). For example, in a case where a film formed on a semiconductor substrate is subjected to plasma etching for forming holes, when an emission spectrum having a specific wavelength is detected, light reflected from an upper surface of the film and a lower surface of the film (the semiconductor substrate and the film). If the light reflected from the interface (light interface) interferes with the photodetector 22, it may not be possible to accurately detect the emission intensity of the emission spectrum. In this embodiment, the focal position of the lens can be shifted by the lens moving means so that such interference light does not enter.

Next, the arithmetic unit 30 for detecting the end point according to the present invention will be described. As shown in FIG. 13, the arithmetic unit 30 receives the input signal from the photodetector 22, that is, the first signal.
The information representing the change in the light emission intensity of the light having the specific wavelength and the signal representing the change in the light emission intensity of the light having the second specific wavelength are calculated, and the ratio of the change in the two light intensities and the ratio of this ratio are calculated. An element extractor 31 for extracting or calculating a differential value (slope)
And the emission intensity ratio (A / A ') on the horizontal axis, and the derivative of the ratio (d (A / A') / dt), that is, the slope on the vertical axis, and the average of the ratio (A / A '). Value and the derivative of the ratio (d (A / A
′) / Dt) in a graph with the intersection with the average value as the origin,
A graphing unit 32 that plots the change of the ratio and the derivative of the ratio with respect to time to create a graph as shown in FIG.
And a slope start determiner 33 that determines a slope start from the created graph, and a slope end determiner 34 that determines the slope end from the created graph. In this preferred embodiment, an origin mover 35 for moving the origin in a graph created when processing the above-mentioned laminated film or a film on a substrate having a step is provided on the output side of the determiners 33 and 34. Have been. These origin movers are driven only when the origin is moved as described above.
Is instructed to repeat the same operation.

More specifically, in the element extractor 31, the following arithmetic processing is performed. (1) Based on the light emission detection information of the first and second active species within the designated period (averaging time), the approximate linear relation A and second linear relationship of the first active species in the relationship between the light emission intensity and time
An approximate linear relation B of the active species is obtained. (2) Using the approximate linear relation A of the first active species and the approximate linear relation B of the second active species, that is, the time-lapse component of the approximate linear relation B of the second active species is converted to the first one. Is substituted into the time-lapse component of the approximation linear relational expression A of the active species to obtain a pseudo approximate linear relational expression A 'of the first active species. (3) From the approximate linear relation A of the first active species and the pseudo approximate linear relation A ′ of the first active species, the ratio (A / A
') And the derivative of the ratio (d (A / A') / dt). (4) The average value and variance value of the ratio (A / A ') and the derivative value (d (A / A') / dt) within the averaging time are obtained.

The graphing unit 32, the slope start determining unit 33, and the slope end determining unit 34 perform the above-described processes, respectively, and perform graph creation, slope start determination, and slope end determination, respectively.

The determination results of the slope start determination and the slope end determination are transmitted to the controller 40, and the etching process is controlled by controlling the high frequency power supply 16 and the like via the controller 40 based on the signal of the determination result. . The result of the slope end determination is sent to the origin mover 35 as necessary, and a signal indicating the result of the origin movement is also sent to the control device 40.

The case where the SiO ₂ film formed on the silicon substrate is actually etched using the CF ₄ gas by using the plasma processing apparatus (plasma etching apparatus) having the above configuration will be described. Here, CO molecules generated by etching SiO ₂ are used as the first active species, and CF ₂ ^* molecules, which are ionized etchants, are used as the second active species. CO molecules were analyzed with a spectroscope, and CF ₂ ^* molecules were filtered with an optofilter. The emission wavelength used for CO molecules is about 219 nm, and the emission wavelength used for CF ₂ ^* molecules is about 260 nm.

First, the optical signal detected and filtered by the photodetector 22 is converted into an electric signal by a photoelectric converter (not shown), and the electric signal is amplified by a preamplifier (not shown).

Next, the amplification factor of the preamplifier for the electric signal of the CO molecule is adjusted to amplify the electric signal of the CO molecule to the same level as that of the CF ₂ ^* molecule. At this stage, both electrical signals are analog signals.

Next, a noise component having a frequency more than twice the sampling cycle, in this case, 20 Hz or more, is cut by a filter. Thereafter, both electric signals are sampled at a cycle of 0.1 second and digitized by an A / D converter.

Next, both digitized electric signals are smoothed by a dynamic averaging method. This has the effect of a so-called low-pass filter, and a relatively smooth signal that does not include high-frequency noise (that is, random noise) is obtained.

Next, in the element extractor 31, an approximate linear relation A of the CO molecule and an approximate linear relation B of the CF ₂ ^* molecule are obtained. FIG. 14 shows straight lines indicating the temporal change of the light emission intensity and the linear relational expression. Using these, a pseudo-approximate linear relationship A ′ of CO molecules is obtained from the approximate linear relationship B of CF ₂ ^* molecules. These relational expressions A,
FIG. 15 shows a time change of the light emission intensity corresponding to B and A ′.

The approximate linear relation A and the pseudo-linear relation A 'both represent the amount of light emitted (intensity) of the CO molecule, and the ratio (A / A') and the derivative of the ratio (d
(A / A ′) / dt). FIG. 16 shows the change over time of the ratio (A / A ′). FIG. 16 shows CO 2 for comparison.
The time variation of the mere ratio (A / B) of the approximate linear relation A of the molecule and the approximate linear relation B of the CF ₂ ^* molecule is also shown.
As is clear from FIG. 16, according to the method of the present invention, since the waveform is flat before and after the end point, the end point can be detected accurately. On the other hand, in the case of a simple ratio (A / B), the waveform is not stable, and the end point cannot be accurately detected due to drift fluctuation.

Next, the ratio (A / A ') is plotted on the horizontal axis, and the differential value of the ratio (d (A / A') / dt) is plotted on the vertical axis, and calculated from information within a designated period (averaging time). Create a graph with the origin as the average of the ratio and the derivative of the ratio. When the ratio and the derivative of the ratio are plotted on the graph, the result is as shown in FIG.

Further, on the graph, the ratio (A / A) calculated from the information of the dispersion tendency obtained within the averaging time.
′) And a predetermined value of the differential value of the ratio (d (A / A ′) / dt), an initial fluctuation range in the graph is obtained.

Next, a position (value) for determining the end point outside the fluctuation range on the graph is set, and the distance from the position to the origin is compared with the radius of the circle of the fluctuation range to obtain a slope start determiner. At 33, a slope start is determined. That is, the ratio (A) is determined using the emission detection information of CO molecules and CF ₂ ^* during the processing after the averaging time.
/ A ') and the derivative of the ratio (d (A / A') / dt), the distance from the position on the graph to the origin, and the light emission detection information within the averaging time. Compare with the radius of the fluctuation range.

More specifically, the square root (D) of the sum of squares of the difference between the ratio corresponding to the position for determining the end point and the differential value of the ratio and the respective average values (origin) is obtained. A point where the ratio (D / C) to the radius (C) becomes larger than a preset threshold value is determined as a slope start.

On the other hand, the slope end is determined by the differential value of the ratio, that is, the slope approaches the horizontal axis again. That is, the slope for determining the end point is compared with a predetermined value based on the dispersion tendency, and the obtained ((slope−average of the slope) / predetermined value) is obtained, and this value is smaller than a preset threshold. When it has become, the slope end determination unit 34 determines the slope end.

According to the end point detecting method of the present invention described above,
Emission light quantity (aperture ratio) is 3 times (1% to 3)
%). In the above embodiment, the first
Using CO molecules as the active species, and C as the second active species
Although the case where an F ₂ ^* molecule is used has been described, the present invention can be applied to a case where another active species is used as the first active species and the second active species.

In the above embodiment, the case where the plasma processing is etching is described. However, in the present invention, the plasma processing is performed by CVD (Chemical Vapor Deposition).
) And PVD (Physical Vapor Deposition).

In the above embodiment, an empirical equation approximating a change in emission intensity of the first active species and the second active species at a specific wavelength with respect to time is used as an approximate linear relationship. It will be obvious to those skilled in the art that the formula is not limited to this. For example, if the change over time changes along an ellipse or part of a hyperbola, these quadratic relations can be used. That is, in the present invention, it is preferable to use an empirical formula that is the closest to the change in the light emission intensity for more accurate measurement.

As the first active species and the second active species,
At the end point of the plasma processing after the designated period, the active species whose intensity is weakened as shown in FIG. 4 and the active species whose intensity is increased as shown in FIG. It is preferable to increase the sensitivity.

As described above, according to the present invention, a direct comparison with the threshold value is not performed, and the predetermined value obtained from the information on the dispersion tendency within the designated period of the plasma processing is used for the determination of the end point. 2. It is possible to sufficiently remove drift fluctuation that cannot be removed by the conventional endpoint detection method using two wavelengths.
Therefore, even if the S / N is poor, the end point can be accurately detected. As described above, since the end of the plasma can be detected accurately, the amount of emitted light (aperture ratio) can be improved three times as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining noise fluctuation of plasma emission intensity.

FIG. 2 is a diagram for explaining drift fluctuation of plasma emission intensity.

FIG. 3 is a diagram for explaining an approximate linear relation between first and second active species and a pseudo approximate linear relation between first active species.

FIG. 4 is a characteristic diagram showing a temporal change in emission intensity (ratio) and slope (differential value).

5 is a graph in which the values shown in FIG. 4 are plotted when the emission intensity (ratio) is plotted on the horizontal axis and the slope (differential value) is plotted on the vertical axis.

FIG. 6 is a diagram for explaining a slope start.

FIG. 7 (A) is emission intensity (ratio) and slope (differential value).
FIG. 4B is a characteristic diagram showing another example of the time change of FIG. 3, and FIG. 4B is a graph plotting the values shown in FIG.

FIG. 8 illustrates an example of an object to be etched.

9A is a characteristic diagram similar to FIG. 7A, showing another example of a temporal change of the light emission intensity (ratio) and the slope (differential value), and FIG. 9B is a light emission intensity. (Ratio) is the horizontal axis,
The graph which plotted the value shown in (A) which made the inclination (differential value) the vertical axis | shaft.

FIG. 10 is a cross-sectional view illustrating another example of an object to be etched.

FIG. 11A is a characteristic diagram showing another example of a temporal change in emission intensity (ratio) and slope (differential value), and
(B) is a graph plotting the values shown in (A), with the emission intensity (ratio) on the horizontal axis and the slope (differential value) on the vertical axis.

FIG. 12 is a view schematically showing a plasma etching apparatus having an end point detection device of the present invention.

13 is a view for explaining an end point detection device in the plasma etching apparatus shown in FIG.

FIG. 14 is a characteristic diagram showing a change over time in emission intensity of CO molecules and CF ₂ ^* .

FIG. 15 is a characteristic diagram showing a temporal change in emission intensity of a CO molecule and CF ₂ ^* after calculation.

FIG. 16 is a characteristic diagram showing a time change of a change rate (ratio) of emission intensity of a CO molecule and CF ₂ ^* .

FIG. 17 is a graph in which the horizontal axis represents the rate of change (ratio) of the emission intensity of CO molecules and CF ₂ ^* , and the vertical axis represents the slope (differential value).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Plasma processing apparatus, 22 ... Photodetector, 30 ... Calculator, 31 ... Element extractor, 32 ... Graphizer, 33 ... Slope start judging device, 34 ... Slope end judging device,
35: origin mover, 40: controller.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/66 H01L 21/66 P

Claims (11)

[Claims] When performing a process using plasma on an object to be processed, an emission intensity of a first active species and a second active species having a specific wavelength is detected during and after a specified period during the plasma process. Outputting the light emission detection information; and, based on the light emission detection information, the approximate relational expression A of the first active species and the approximate relational expression B of the second active species in relation between the light emission intensity and time. Obtaining a pseudo-approximate relational expression A 'of the first active species using the approximate relational expression A of the first active species and the approximate relational expression B of the second active species; From the approximate relational expression A of the first active species and the pseudo approximated relational expression A ′ of the first active species, the ratio (A / A ′) between them and the differential value of the ratio (d (A / A ′) / dt) ), And the ratio (A / A ′) within the designated period and the differential value of the ratio d (A / A') / dt) of the step of obtaining the respective mean value and the variance tendency, the ratio (taken A / A') a horizontal axis, the ratio of the differential value (d
(A / A ') / dt) is plotted on the vertical axis, and the average value of the ratio (A / A') and the differential value of the ratio (d (A
/ A ′) / dt) is plotted on the graph with the intersection point with the average value as the origin, and the ratio (A / A) calculated from the dispersion tendency information is plotted on the graph.
') And the derivative of the ratio (d (A / A') /
setting a predetermined area from a predetermined value of dt); and setting the first and second areas during processing after the specified period.
The ratio (A / A ') and the derivative of the ratio (d (A / A') / dt) are obtained using the emission detection information of the active species of the above, and the obtained ratio (A / A ') and the derivative of the ratio are obtained. Value (d (A / A ') /
dt) determining when the position in the graph deviates from the predetermined area as the end point of the plasma processing;
A method for detecting an end point of a plasma process, comprising: 2. The predetermined area includes a predetermined value of the ratio (A / A ′) calculated from information on the dispersion tendency in the specified period and a differential value of the ratio (d (A / A ′) / dt). 2. The method according to claim 1, wherein the predetermined value is set by a square root r ₁ of a sum of squares of the predetermined value. 3. A differential value of the ratio (A / A ′) calculated from the dispersion tendency information using a maximum value of a difference between the ratio and an average value of the ratio as a predetermined value of the ratio (A / A ′). d (A / A
2. The method according to claim 1, wherein the maximum value of the difference between the differential value of the ratio and the average value of the differential value of the ratio is used as the predetermined value of ') / dt). 4. The step of determining an end point of the plasma processing includes the following steps:
A predetermined value of the ratio (A / A ′) calculated from the information of the dispersion tendency in the specified period and a differential value of the ratio (d (A /
A ′) / dt), the square root r _{1 of the} sum of squares of the predetermined value, the calculated ratio (A / A ′) and the differential value of the ratio (d (A /
A') / dt) wherein comparing the distance r ₂ between the position and the origin in the graph of, the end point of the plasma processing when the distance r ₂ is greater than the square root r ₁ of the square sum of the dispersion 2. The method according to claim 1, further comprising the step of determining.
Method for detecting the end point of the plasma treatment of the above. 5. The step of determining an end point of the plasma processing,
A predetermined value of the ratio (A / A ′) calculated from the information of the dispersion tendency in the specified period and a differential value of the ratio (d (A /
A ′) / dt) calculates the square root r ₁ of the sum of squares of the predetermined value, and the values of the horizontal axis component and the vertical axis component of the coordinates in the graph are both greater than the square root r ₁ of the square sum of the predetermined value. 2. The method according to claim 1, further comprising the step of determining an end point of the plasma processing when the end point is reached. 6. A point at which the position of the calculated ratio (A / A ′) and the derivative of the ratio (d (A / A ′) / dt) in the graph again intersects the horizontal axis of the graph is defined as an origin. ,
A predetermined value of the ratio (A / A ') and a derivative of the ratio (d (A
/ A ′) / dt) to set another predetermined area from the predetermined value,
The first and the second during the processing after the designated period
The ratio (A / A ') and the derivative of the ratio (d (A / A') / dt) are obtained using the emission detection information of the active species of the above, and the obtained ratio (A / A ') and the derivative of the ratio are obtained. Value (d (A / A ') /
2. The method according to claim 1, further comprising the step of determining when the position in the graph of (dt) deviates from the other predetermined area as another end point of the plasma processing. 7. When performing a process using plasma on an object to be processed, the emission intensity at a specific wavelength of light emission from the first and second active species during a specified period during the plasma process and thereafter. Outputting the light emission detection information by sequentially detecting the light with the light detection means; and, based on the light emission detection information within the designated period, an approximate relational expression A and a second relational expression of the first active species in the relation between the light emission intensity and time. Calculating the approximation relational expression B of the active species, and the pseudo approximation relational expression of the first active species using the approximation relational expression A of the first active species and the approximation relational expression B of the second active species A step of obtaining A ′, and a ratio (A / A ′) of the two and a differential value of the ratio (A / A ′) from the approximate relational expression A of the first active species and the pseudo approximate relational expression A ′ of the first active species. d (A / A ′) / dt); and the ratio (A) within the designated period. / A ′) and the average value and dispersion tendency of the differential value (d (A / A ′) / dt) of the ratio, and the ratio (A / A ′) on the horizontal axis. Derivative value (d
(A / A ') / dt) is plotted on the vertical axis, and the average value of the ratio (A / A') and the differential value of the ratio (d (A
/ A ′) / dt) is plotted on the graph with the intersection as the origin, and the ratio (A) obtained using the emission detection information of the first and second active species during the processing after the designated period is obtained.
/ A ′) and the time when the position of the differential value of the ratio (d (A / A ′) / dt) in the graph deviates from the origin and approaches the horizontal axis again as the end point of the plasma processing. A method for detecting an end point of a plasma process, comprising: 8. During processing using a plasma for an object to be processed,
Detecting the emission intensities of the first and second active species generated by the plasma at respective specific wavelengths during and after a designated period during processing, and outputting the emission detection information; , An approximate relational expression A of the first active species and an approximate relational expression B of the second active species that represent a straight line or a curve approximating the change in emission intensity over time.
And substituting the elapsed time of the approximation relational expression B of the second active species into the elapsed time of the approximation relational expression A of the first active species to obtain a pseudo approximate relational expression A ′ of the first active species. From the approximation relational expression A of the first active species and the pseudo approximation relational expression A ′ of the first active species, a ratio (A / A ′) of the two and a differential value (d ( A / A ′) / dt), and the average and variance of the ratio (A / A ′) and the derivative of the ratio (d (A / A ′) / dt) within the specified period. Calculating the tendency; taking the ratio (A / A ') on one axis of the rectangular coordinate system; taking the differential value (d (A / A') / dt) of the ratio on the other axis; A graph having an origin at the intersection of the average value of the ratio (A / A ') and the average value of the differential value (d (A / A') / dt) of the ratio is prepared. Setting a predetermined area from a predetermined value of the ratio (A / A ′) and a predetermined value of a differential value of the ratio (d (A / A ′) / dt) roughly calculated from the information on the dispersion tendency; The first and the second during the processing after the designated period
The ratio (A / A ') and the derivative of the ratio (d (A / A') / dt) are obtained using the emission detection information of the active species of the above, and the obtained ratio (A / A ') and the derivative of the ratio are obtained. Value (d (A / A ') /
dt) determining when the position in the graph deviates from the predetermined area as the end point of the plasma processing;
A method for detecting an end point of a plasma process, comprising: 9. The step of obtaining the approximate relational expression A of the first active species and the approximate relational expression B of the second active species,
Calculating the approximate linear relation A of the active species and the approximate linear relation B of the second active species. The step of determining the pseudo approximate relation A ′ of the first active species comprises: A step of obtaining a pseudo-approximate linear relation A ′ of the first active species using the approximate linear relation A of the first kind and the approximate linear relation B of the second active species, wherein the ratio (A / A ′) ) And the derivative of the ratio (d (A / A
') / Dt) is obtained by calculating the ratio (A / A') of the two from the approximate linear relation A of the first active species and the pseudo approximate linear relation A 'of the first active species. 9. The method according to claim 1, further comprising the step of obtaining a differential value (d (A / A ') / dt) of the ratio. 10. An active species whose emission intensity becomes weaker and an active species whose intensity becomes weaker at the end point of the plasma treatment after a designated period are used as the first active species and the second active species. The method according to any one of claims 1 to 9, wherein the end point of the plasma processing is detected. 11. A method for detecting a change in emission intensity of a first and second active species at a specific wavelength with respect to time, which is generated by plasma when performing a process using plasma on an object to be processed, and performs emission detection information. A light detection unit, and an approximate relational expression A of the first active species and an approximate relational expression B of the second active species are determined in the relationship between the light emission intensity and the time based on the light emission detection information within the designated period; Using the approximate relational expression A of the first active species and the approximate relational expression B of the second active species, a pseudo approximate relational expression A ′ of the first active species is obtained, and the approximate relational expression of the first active species is obtained. From A and the pseudo-approximate relational expression A ′ of the first active species, the ratio (A / A ′) of both of them and the differential value (d (A / A ′) / dt) of the ratio are obtained, and within the specified period Of the ratio (A / A ′) and the derivative of the ratio (d (A / A ′) / dt) A calculating means for calculating the average value and dispersion tendency, the horizontal axis the ratio (A / A'), the ratio of the differential value (d
(A / A ′) / dt) is plotted on the vertical axis, and the ratio (A / A ′)
') And the differential value of the ratio (d (A / A') / d
graphing means for creating a graph with the origin at the intersection with the average value of t); a predetermined value of the ratio (A / A ') calculated from the information of the dispersion tendency and a differential value of the ratio (d (A / A ') / dt)
A predetermined area is set from a predetermined value of the ratio (A / A ′) and a differential value of the ratio (d (A)) using the emission detection information of the first and second active species during the processing after the specified period. /
A ′) / dt) is determined, and when the determined ratio (A / A ′) and the derivative of the ratio (d (A / A ′) / dt) in the graph deviate from the predetermined region, the plasma is determined. An end point detection apparatus for plasma processing, comprising: determination means for determining an end point of processing.