JPH06318572A - Method and apparatus for detecting end point of plasma treatment - Google Patents

Abstract

PURPOSE:To detect an end point accurately even on different plasma treatment conditions by letting a point when a ratio of a mean value and a dispersed value of a generation strength of a specified wave length of an emission spectrum within a specified period of time to a calculated value of a generation strength after the specified period of time and the said mean value and a dispersed value exceeds a specified reference value be an end point. CONSTITUTION:This equipment is provided with a treatment chamber 11 formed of conductive material such as aluminum, a lower electrode 12, and an upper electrode 13 which is placed above and apart from the lower electrode 12. A gas lead-in pipe 14 for leading in fluorocarbon-system etching gas such as CF is connected to the upper part of the treatment chamber 11 and an exhaust pipe 15 is also connected to the treatment chamber 11. The upper electrode 13 is connected to a high-frequency source 16. Outside a window 17, a lens 21 for condensing transmitted light and a photo detector 22 are placed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing end point detecting method and apparatus.

[0002]

2. Description of the Related Art An etching apparatus using plasma has been widely applied to a semiconductor manufacturing process or a liquid crystal display substrate manufacturing process. Such an etching apparatus is provided with, for example, an upper electrode and a lower electrode arranged in parallel with each other, and a plasma is generated from the etching gas by the discharge between the upper electrode and the lower electrode. A semiconductor wafer as an object to be processed is etched. During the etching process, the progress of the etching is monitored, the end point thereof is detected as accurately as possible, and the etching process is performed according to a predetermined pattern.

Conventionally, instrumental analysis methods such as mass spectrometry and spectroscopic analysis have been used as methods for detecting the end point of etching, and among them, comparatively simple and highly sensitive spectroscopic analysis is widely used. . When a spectroscopic method is used to detect the end point of etching, specifically, a specific active species among active species such as etching gas, radicals such as decomposition products or reaction products thereof, or ions are used. Then, the emission intensity of the emission spectrum of the selected active species is measured. In this case, the selected active species depends on the type of etching gas. For example, when a silicon oxide film is etched using a fluorocarbon-based etching gas such as CF ₄ , the reaction product CO
Emission spectrum from ^* (219 nm or 483.5 nm
Etc.), and when the silicon nitride film is etched using a fluorocarbon-based etching gas such as CF ₄ , the emission spectrum (674 nm etc.) from N ^* that is the reaction product is measured. . Then, the end point of etching is determined by comparing the amount of change in the emission intensity of the specific wavelength, the primary differential value, the secondary differential value, etc. of the intensity with a preset threshold value.

[0004]

However, in the case of the conventional end point detection method, the active species for measuring luminescence is different depending on the individual process, for example, the type of the film to be etched. You have to set the threshold again each time. Further, even if the kinds of films to be etched are the same, if the etching conditions are different due to the difference in film thickness and the like, the threshold value corresponding to each etching condition must be reset each time. In order to set these thresholds, it is necessary to set numerical values based on a complicated mathematical formula.

The present invention has been made to solve the above problems, and it is not necessary to reset the threshold value each time according to each process or each object to be processed, and it is possible to accurately perform plasma under different plasma processing conditions. It is an object of the present invention to provide a versatile end point detection method and apparatus capable of detecting the end point of processing.

[0006]

According to the present invention, a step of sequentially detecting an emission spectrum of an active species having a specific wavelength in the plasma by a photodetecting means, when the object to be treated is treated with the plasma, Obtaining an average value and a dispersion value of the emission intensity of the emission spectrum within an initial predetermined time period of plasma treatment, and obtaining a calculated value by calculating a difference between the average value and the emission intensity after the initial predetermined time period has elapsed, Further, there is provided an end point detection method comprising a step of comparing the calculated value and the dispersion value and determining a time point when the calculated value exceeds a predetermined reference value as an end point of the plasma processing.

Further, according to the present invention, the emission intensity of the emission spectrum obtained by detecting the emission spectrum of the active species having a specific wavelength generated when the object to be treated is treated with plasma by the photodetector. An average value / dispersion value calculating means for obtaining the average value and the dispersion value based on the above, a calculating means for obtaining the difference between the average value and the emission intensity from the average value / dispersion value calculating means, and the calculating means Comparing means for comparing the calculated value with the dispersion value from the average value / dispersion value calculating means, and judging means for judging the time when the calculated value exceeds a predetermined reference value as the end point of the plasma processing by the comparing means. An end point detection device is provided which detects the end point of plasma processing based on a change in emission intensity of the emission spectrum.

[0008]

According to the present invention, the emission spectrum is sequentially detected by the photodetector within the predetermined time T _{1 at the} beginning of the plasma treatment, the average value and the dispersion value of the emission intensity of the specific wavelength of the emission spectrum are obtained, and the predetermined time is reached. After the elapse of T ₁ , the calculated value of the emission intensity at that time and the above-mentioned average value is obtained, then the ratio of this calculated value and the above-mentioned dispersion value is obtained, and when the ratio exceeds a predetermined reference value, the plasma treatment is performed. Judge as the end point.

Further, according to the present invention, the emission intensity I and the first-order differential value of its waveform are converted into XY coordinates. The origin O of the XY coordinates is set to the initial average value of the emission intensity I (X coordinate value) and the slope of the waveform within a predetermined time period of the initial plasma processing. As a position at which the current coordinates start to suddenly separate from the origin O, a position where the distance L between the origin O and the current coordinates is larger than a predetermined threshold value Ls can be used,
The position is determined as the end point of the plasma processing.

[0010]

Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 is an explanatory diagram showing the structure of a plasma processing apparatus equipped with an end point detecting device according to the present invention. The plasma processing apparatus 10 includes, for example, a processing chamber 11 made of a conductive material such as aluminum, and a lower electrode 12 which is disposed in the processing chamber 11 and also serves as a mounting table on which a semiconductor wafer W to be processed is mounted. And an upper electrode 13 disposed above the lower electrode 12 and separated from the lower electrode 12.

A gas introduction pipe 14 for introducing a fluorocarbon-based etching gas such as CF ₄ is connected to the upper portion of the processing chamber 11. Further, an exhaust pipe 15 for discharging the generated gas is connected to the side wall of the processing chamber 11. The lower electrode 12 is grounded and is always kept at the ground potential. The upper electrode 13 is connected to a high frequency power supply 16, and a high frequency voltage is applied from the high frequency power supply 16 to cause discharge between the lower electrode 12 and the upper electrode 13, thereby activating the etching gas and radical species. , Plasma P composed of active species such as ionic species is generated.

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 this window 17 and the transmitted light is analyzed. By doing so, the progress of etching is monitored. A lens 21 for condensing transmitted light is arranged outside the window 17, and a photodetector 22 for detecting and photoelectrically converting the light condensed by the lens 21 is provided at the subsequent stage of the lens 21. It is arranged. The photodetector 22 is composed of, for example, an interference filter or a spectroscope and a photomultiplier or a photodiode,
After the light of a specific wavelength is separated by an interference filter or a spectroscope, the separated light of a specific wavelength is photoelectrically converted and the emission intensity I is transmitted as an electric signal. An end point of etching is detected by an end point detection device 30 described later based on an electric signal corresponding to the emission intensity transmitted from the photodetector 22, and a control signal is transmitted to the control device 40 when the end point is detected. Plasma processing apparatus 1 via controller 40
The etching is completed by controlling 0.

Here, the position of the lens 21 can be appropriately moved by the lens moving means 21a. For example,
When plasma-etching a film formed on a semiconductor substrate, when the emission spectrum having a specific wavelength is detected, the light reflected on the upper surface of the film and the lower surface of the film (interface between the semiconductor substrate and the film) are reflected. If the light interferes with the light, it may not be possible to accurately detect the emission intensity of the emission spectrum. By appropriately changing the focal position of the lens by the lens moving means 21a, such a phenomenon can be reduced and the emission intensity of the emission spectrum can be accurately detected. In this case, since the film thickness changes as the etching progresses, it is preferable to appropriately change the focal position of the lens according to the rate of decrease in the film thickness.

Next, the end point detecting device 30 according to the present invention will be described with reference to FIGS. As shown in FIG. 2, the end point detection device 30 of the present invention uses an input signal from the photodetector 22, that is, a waveform of the emission intensity I to determine its intensity I.
And a detection element extractor 31 for extracting and transmitting detection elements such as the first derivative (slope) of a waveform, and this detection element extractor 31.
An average value / variance value calculator 32 for calculating the average value m and the variance value σ ² from the emission intensity I (see FIG. 3) sequentially extracted by the above, and the average value / variance value calculator 32 Average value m received from the detection element extractor 31
Calculator 33 for calculating and transmitting the difference from the emission intensity I received from the calculator 33, the calculated value (difference value) received from the calculator 33, and the variance value σ received from the average value / dispersion value calculator 32.
A comparator 34 for comparing ² and transmitting the comparison result,
The determination unit 35 determines that the time point when the absolute value of the comparison value received from the comparator 34 exceeds a predetermined reference value is the etching end point. The determination result of the determiner 35 is transmitted to the control device 40 as described above, and the high frequency power supply 1 is transmitted via the control device 40 based on the signal of the determination result.
The etching process is controlled by controlling 6 and the like.

Next, a method of detecting an end point using the end point detection device of the present invention will be described. First, the average value / dispersion value calculator 32 calculates the average value m and the dispersion value σ ² of the emission intensity I of the plasma P within the predetermined time T _{1 at the} beginning of etching.
Then, the variation of the emission intensity I due to the gas amount of the etching gas during the etching process or electric noise is statistically grasped. Then, this initial predetermined time T
After _one lapse, the difference between the light emission intensity I and the average value m that fluctuates over time is calculated by the calculator 33, and then the absolute value of this difference and the variance σ ² are compared by the comparator 34. The time when this absolute value exceeds the reference value is determined by the determiner 35 as the etching end point.

The initial predetermined time T ₁ of etching in the above-described end point detection is a time that can be arbitrarily set within a fixed time from the time when etching is started to the time when etching is finished, and usually various etchings are performed. A time within a range common to various etching processes, which is not influenced by the processing conditions, is set. This initial predetermined time T ₁
By obtaining the average value m and the variance value σ ² of the waveform of the luminescence intensity I that fluctuates within the time point when the initial predetermined time T _{1 has} elapsed, the upper and lower limits of the temporal variation of the luminescence intensity I during the etching process are grasped at the initial stage of etching. can do. Further, when the difference value between the emission intensity I and the average value m and the variance value σ ² are compared after the lapse of an initial predetermined period, the standard deviation σ of the variance value σ ² is used when the difference value is directly compared. . It is possible to recognize the time point when the comparison value exceeds the reference value after the lapse of the initial predetermined period as the end point of the etching process. That is, it is possible to use the average value m and the variance value σ ² calculated each time under the respective etching conditions as described above as the reference value when the deciding device 35 decides the end point, that is, the threshold value.

Next, the operation of the end point detection device 30 will be described with reference to the flow chart shown in FIG. For example, a semiconductor wafer W having a silicon oxide film formed thereon is placed on the lower electrode 12 in the processing chamber 11 in which a vacuum state of 0.1 mTorr to several Torr is formed. Next, a high-frequency voltage is applied to the upper electrode 13 by the high-frequency power source 16 to apply the high-frequency voltage to the lower electrode
To discharge between. Furthermore, an etching gas containing CF ₄ as a main component is supplied from the gas introducing pipe 14 to the processing chamber 11
It is supplied into the inside and CF ₄ or the like is turned into plasma to generate active species. When the silicon oxide film of the semiconductor wafer W is etched by this active species, SiF ₄ and CO ^* which is an active species for monitoring are produced. The respective emission spectra generated when the active species such as CO ^* return to the ground state are transmitted through the window 17 of the processing chamber 11, condensed by the lens 21, and reach the photodetector 22. The photodetector 22 disperses a CO ^* emission spectrum (483.5 nm or the like) from the detection light having a plurality of emission spectra, and then transmits an electric signal of photoelectrically converted emission intensity I as a data signal to the end point detection device 30. To do.

As shown in FIG. 4, when the end point detecting device 30 receives a data signal, it performs the following processing internally. That is, the detection element extractor 3 of the end point detection device 30
At 1, the data signal is received as input data (S ₁ ).
Next, the detection element extractor 31 extracts input data based on the emission intensity I from the received input data (S
₂ ) It is judged whether or not this reception is within the initial predetermined time T _{1 of} etching (S ₃ ), and if it is within the initial predetermined time T ₁ , it is sequentially transmitted to the average value / variance value calculator 32, and these Only input data is stored (S ₄ ). After that, the process returns to S ₁ and these series of operations are repeated to successively accumulate the input data. After that, if it is determined in S ₃ that the initial predetermined time T ₁ is not reached, the process proceeds to S ₅ , it is determined whether or not the initial predetermined time T ₁ has just been reached, and it is just the end of the initial predetermined time T _1. If it is determined that the average value / variance value calculator 3
The average value m and the variance value σ ² of the emission intensity I are calculated by the average value / variance value calculator 32 based on the input data accumulated in step ² (S ₆ ), and then the process returns to step S ₁ . When it is determined in S ₅ that the initial predetermined time T ₁ has elapsed, signals of the average value m and the variance value σ ² are transmitted from the average value / variance value calculator 32 to the calculator 33 and the comparator 34, respectively at that time. . This arithmetic unit 33 stores this average value m, finds the difference between the input data successively received from the detection element extractor 31 and the average value m (S ₇ ), and outputs the signal of this difference value to the successive comparator 34. Send to. The comparator 34 successively compares the already stored variance value σ ² (more specifically, the standard variation σ) with the value of this difference (S ₈ ), and sends the result to the determiner 35. . The determiner 35 sequentially determines whether or not the absolute value of the difference exceeds the reference value based on the comparison result sequentially received (S ₉ ), and if not, returns to S ₁ and repeats the determination. On the other hand, if it is determined in S ₉ that the absolute value exceeds the reference value, it is determined that the etching end point has been reached, and a control signal is transmitted to the control device 40 to end the etching process.

As described above, according to the present embodiment, within the initial predetermined time T _{1 of} etching, the average / dispersion value calculator 32 successively receives the emission intensity I from the detection element extractor 31 and accumulates it. The average value m and the variance value σ ² of the emission intensity data are obtained based on the data signal of the above, and after the lapse of the initial predetermined time T ¹ , the calculator 33, the comparator 34 and the determiner 3
5 is a detection element extractor 31 and an average value / variance value calculator 3
Since the etching end point is determined on the basis of the data signals respectively received from 2, ie, the emission intensity I, the average value and the dispersion value σ ² , for example, slight fluctuations in the etching processing conditions such as the inflow amount of the etching gas and the like. Even if the waveform of the emission intensity I fluctuates as shown in FIG. 3 due to electrical noise and is in an unstable state, the electrical signal transmitted from the photodetector 22 causes the emission intensity I to fluctuate up and down during the etching process. It is possible to make a sharp distinction between vertical fluctuation at the end of etching. This makes it possible to accurately detect the end point of etching and perform predetermined etching. Therefore, unlike the conventional case, it is not necessary to set a threshold value to suit each condition every time the etching condition changes, and the etching end point can be detected efficiently and accurately even under different etching process conditions.

In this embodiment, the emission intensity I of the light emitted when the excited molecules in the plasma P return to the ground state.
However, the present invention is not limited to the emission intensity, and the first derivative of the curve that can be drawn when the emission intensity is measured with time or The second-order differential value may be similarly statistically processed to obtain the end point. Further, although the case of the etching process is described in the present embodiment, the end point detection method and apparatus of the present invention are not limited to the end point detection of the etching process, and light emission occurs as the plasma process progresses like an asher device. It can be applied to the case where the spectrum is changed. (Embodiment 2) In the case of the conventional end point detecting method, since the end point of etching is detected by using one detecting element, when the detecting element changes only a minute amount, the etching gas The fluctuation amount of the detection element is absorbed by the fluctuation of the etching condition due to a slight pressure change or the electric noise, and it becomes difficult to distinguish the fluctuation amount of the latter from the fluctuation amount of the former, and the end point can be accurately detected. There is a problem of disappearing.

Further, in the case of the conventional end point detection method, one of the detection elements such as the emission intensity I is compared with a preset threshold value during the etching process, so that the end point may be different depending on the etching portion. Differently, if the emission intensity waveform fluctuates with a plurality of steps, or if it has a convex or concave waveform generated from a complicated multilayer film structure in which different types of films are layered, the end point depends on the number of steps. Therefore, it becomes difficult to determine the end point at each step, and it becomes more and more impossible to accurately detect the end point. For example, when the light emission intensity I is selected as the detection element, the light emission intensity I varies depending on the etching conditions such as gas flow rate, gas type, pressure, and electric power.
The waveform I ₁ and the second waveform I ₂ after the end of etching are
As shown in FIG. 5, the threshold value s of the slope-shaped third waveform I ₃ indicating the end point of the etching is not the _third value because the threshold value s is the third value.
If the waveform I _{3 is in} the vicinity of the initial or final stage, the threshold s may not be discriminated from the first waveform I ₁ or the second waveform I ₂ . Therefore, a stable determination of the end point cannot be performed depending on the etching processing conditions.

In the present embodiment, the fluctuation of the light emission intensity during etching can be detected two-dimensionally, and the end point of etching can be accurately detected with almost no influence from electrical noise. Thus, even if the etching film thickness varies from part to part, an end point detecting method and an end point detecting device capable of continuously and accurately detecting the etching end point according to each film thickness are provided.

The end point detection device 30 of this embodiment will be described with reference to FIGS. As shown in FIG. 6, the end point detection device 30 of the present embodiment shows, from the waveform of the input signal from the photodetector 22, that is, the waveform of the emission intensity I, the emission intensity I and the first derivative (slope) of the waveform in FIG. As shown, a coordinate converter 41 for converting to XY coordinates, and this coordinate converter 4
The distance L between the origin O of the XY coordinates coordinated by 1 and the current coordinate is compared with a predetermined threshold Ls, and the point where the distance L exceeds the threshold Ls (see FIG. 8B) is set as the change start of the emission intensity I. Inflection point (change start point) S (Fig. 8)
A)) and a point where the point is the end point, and the point where the first derivative of the current coordinate, which shows the inclination after the change start, rapidly approaches the X coordinate axis, that is, as shown in FIG. 8B. The point at which the X coordinate value (emission intensity) hardly changes and the Y coordinate value (slope) approaches 0 is set as the end inflection point (change end point) E (see FIG. 8A) as the change end, and FIG. 10 shows the change end judging device 43 that judges this point as the end point and the end point judged by this change end judging device 43.
A and new origin O _{1 of} XY coordinates as shown in FIG. 10B.
And an origin moving device 44 for moving the origin O to the new origin O ₁ . It should be noted that the threshold value Ls is a dispersion value of X (emission intensity) where S _X is
When S _Y is a variance value of Y (slope) and A is an arbitrary constant, it can be obtained by the following formula (I).

[0024]

[Equation 1]

The coordinate converter 41 converts the value of the emission intensity I and the inclination into the X coordinate value and the Y coordinate value, respectively, based on the input signal from the photodetector 22, and on the XY coordinate shown in FIG. The locus of the emission intensity I and the inclination is drawn, and the initial values of the emission intensity I and the inclination or the respective initial average values at the respective initial predetermined times are set as the origin O of the XY coordinates. This initial predetermined time is a time that can be arbitrarily set within a fixed time from the time when the etching is started to the time when the etching is ended, and such a time depends on various etching processing conditions. It is possible to set a time within a range common to various etching processes. Further, the change start judging device 42 receives the signal from the coordinate converter 41 and recognizes the present coordinates, thereby judging the etching end point as described above, and constantly transmitting the judgment result to the control device 40. Then, the plasma processing apparatus 10 is controlled. Further, the change end determination unit 43 compares the inclination (Y coordinate value) of the current coordinates, which has received the signal from the coordinate converter 41, with the threshold value (a numerical value as close as possible to 0 on the Y coordinate) to determine the change end point E. By recognizing, the end point of etching is determined as described above, but the determination result is transmitted to the origin moving unit 44. The origin moving unit 44 uses a resist layer 52 as a film 51 formed on a substrate 50 having a different film thickness to be etched, for example, as shown in FIG.
10A when the openings 53a to 53c having different depths are formed by etching using the mask as a mask.
As shown in FIG. 6, the change occurs when the emission intensity waveform gradually decreases after etching of each portion, or when the waveform changes to a convex shape (see FIG. 13A) or a concave shape (see FIG. 13C). When the signal from the end determiner 43 is received and the waveform changes, the change end determiner 43
The origin O is continuously moved to a new origin O ₁ at each stage where the waveform is changed.

Here, when the waveform of the emission intensity I changes to a convex shape as shown in FIG. 13A, for example, as shown in FIG. 12, the SiO ₂ film 61 and Si are formed on the semiconductor substrate 60.
_{In the} same step, CH films are formed by sequentially stacking ₃ N ₄ films 62.
There is a case where the opening 63 is formed by etching using an etching gas such as F ₃ + CF ₄ + Ar + O ₂ .

Next, an embodiment of the end point detecting method using the end point detecting device of this embodiment will be described. In the end point detection method of this embodiment, first, the emission spectrum when the semiconductor wafer W is etched using the plasma P is sequentially detected by the photodetector 22, and based on the change in the emission intensity of the emission spectrum at the specific wavelength. When detecting the end point of etching, the emission intensity I and the first-order differential value of its waveform are converted into XY coordinates by the coordinate converter 41 as shown in FIG. 7, and the current coordinate value is XY at this XY coordinate. Origin of coordinates O
Is determined as the end point of etching.

More specifically, the origin O of the XY coordinates at this time is the emission intensity I (X
(Coordinate value) and the initial average value of the slope of the waveform. Then, as a position where the current coordinates start to be suddenly separated from the origin O described above, a position where the distance L between the origin O and the current coordinates is larger than a predetermined threshold value Ls (see FIG. 8B) can be used. Is set as the change start point S of the emission intensity I, and this change start point S is used as the end point of the etching, and the change start determination unit 42 determines. Therefore, during the etching process, the emission intensity I is not constant as shown in FIG. 13A and FIG. 13B as described above, and it fluctuates up and down and is not stable. Therefore, the current coordinates on the XY coordinates are the X coordinate value and the Y coordinate. The coordinate values are shown in Figure 8B.
As shown in, the center of the origin O is continuously changed within the range of the threshold value Ls, and the origin O is spirally moved. However, immediately before the etching process is completed, the emission intensity I sharply decreases, and thus a slope as shown in FIG. 8A is drawn. When the X coordinate value (light emission intensity) sharply decreases from the change start point S, the current coordinate deviates from the threshold value Ls on the XY coordinate as shown in FIG. 8B. The change start determiner 42 determines the position at that time as a change start point S, and detects the point S as the end point of etching. Next, the current coordinate passes the change start point S, and then moves downward in the minus (negative slope) region of the Y coordinate value and decreases to less than the initial average value of the emission intensity I and moves to the minus region of the X coordinate. A downward curving path is drawn from the X-axis toward the change end point E shown in FIG. 8A. The threshold value Ls is preferably an integer multiple of the variance value σ ² .

On the other hand, when the end point of etching is detected at the change end point E, the point at which the current coordinate curve downward from the X axis approaches the X axis after the change start, that is, the slope of the emission intensity I, A point approaching Y = 0 or a point that becomes smaller than the variance value of the inclination is determined as a change end point E by the change end determiner 43, and this change end point E is detected as the etching end point. Next, after the change end point E at which the etching is completed, the emission intensity I is stable in the lower part although it fluctuates vertically as in the etching process. Therefore, the current coordinate is centered on the coordinate value ( _IE , 0). Draw a trajectory that moves in a spiral fashion.

As described above, according to the present embodiment, the specific wavelength from the plasma P during the etching process is separated and continuously received, and the intensity I and the slope of the emission intensity waveform of this received light are XY. By making the coordinates, the end point of the etching is detected by utilizing the two-dimensional variation of the light emission intensity I and the inclination.
Can be detected two-dimensionally by the emission intensity I and the slope of its waveform, and the end point of etching can be accurately detected with almost no influence of electrical noise.
When the specific wavelength of the plasma P of the etching gas is monitored, the gas is consumed during etching,
The emission intensity I stabilizes at the lower level, but after the end point of etching, gas consumption disappears and the emission intensity I rises sharply and changes as shown in FIGS. 11A and 11B. Can be detected.

Further, as shown in FIG. 9, when the films 51 having different film thicknesses to be etched are etched in the same step, the etching is sequentially completed from the thinnest portion to the thickest portion. The emission intensity I gradually decreases as the etching of each part is completed, as shown in FIG. 10A. This phenomenon occurs even when a plurality of types of films having different film thicknesses are etched in the same process. That is,
The emission intensity I gradually decreases as the etching is sequentially completed from the thinnest film to the thickest film. Further, even if the film thickness is the same, when the dimensions of the regions to be etched are different from each other, since the etching is sequentially finished from the portion having the smallest dimension (area) to the portion having the largest dimension, the emission intensity I Also decreases gradually as the etching of each portion is completed, as shown in FIG. 10A. Furthermore, this occurs even when a plurality of types of films having different etching rates are etched in the same process. That is, the emission intensity I gradually decreases each time the etching is sequentially completed from the film having the highest etching rate to the film having the lowest etching rate.

In this case, when the first etching is completed, the change end determination unit 43 detects the etching end point as described above, and the detection signal is transmitted to the origin moving unit 44. The origin moving unit 44 operates based on the received signal, and sets the end point immediately after the change end, that is, the position indicating the initial average value of the light emission intensity I and the slope of the waveform at the initial predetermined time at this stage to X-. It is set as a new origin O ₁ of the Y coordinate, and the first origin O is moved to the new origin O ₁ . At this stage, as described above, the end point of etching at this stage is determined from the change end point E, and the same operation is repeated thereafter to sequentially move the origin. When all etching is completed, the origin moving unit 44 sends an etching end point signal to the control device 40 to end the etching.

In addition, whether the waveform of the emission intensity I changes to a convex shape as shown in FIG. 13A or a concave shape as shown in FIG. 13B, the origin O is changed to a new origin O ₁ as shown in FIG. 13B at each stage where the waveform changes.
When moved each time, the current coordinate draws a substantially symmetrical locus about the Y-axis.

As described above, even when the film thickness of the etching on the wiring structure varies depending on the part, the change end judging device 43 and the origin moving device 44 operate to continuously and accurately determine the etching end points according to the respective film thicknesses. Can be detected. In this embodiment, the case where the change end determination unit 43 transmits a signal to the origin moving unit 44 has been described, but the change start determination unit 42 can also transmit a signal to the origin moving unit 44.

In this embodiment, the case of the etching process is explained, but the end point detection method and apparatus of the present invention is not limited to the end point detection of the etching process, and the emission spectrum of the emission process increases as the plasma process progresses. In the case where there is a change, the end point detection method and apparatus of the present invention can be applied.

[0036]

As described above, the method and apparatus for detecting the end point of the present invention obtain the average value and the dispersion value of the emission intensity of the emission spectrum within the initial predetermined time of the plasma processing, and after the initial predetermined time has passed, the average value and the dispersion value are calculated. The difference between the emission intensity is calculated to obtain the calculated value, the calculated value and the variance value are compared, and the time when the calculated value exceeds the predetermined reference value is determined as the end point of the plasma processing. It is not necessary to reset the threshold value corresponding to the end point according to the body, and the end point of the plasma processing can be accurately detected even under different processing conditions.

Further, the end point detecting method and apparatus of the present invention convert the emission intensity and the slope of the waveform of the emission intensity into XY coordinates based on the information from the emission spectrum, and newly generate X-
Since the point at which the Y-coordinated point is abruptly separated from the origin of the XY coordinate is determined as the end point of the plasma processing, fluctuations in the emission intensity during the plasma processing are detected two-dimensionally and the influence of electrical noise is detected. Can be removed to accurately detect the end point of the plasma treatment.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a main part of a plasma processing apparatus provided with an embodiment of an end point detection device according to the present invention.

FIG. 2 is a block diagram showing the configuration of the end point detection device shown in FIG.

FIG. 3 is a graph for explaining the operation of the end point detection device shown in FIG.

4 is a flowchart showing a position embodiment of an end point detection method according to the present invention using the end point detection device shown in FIG.

FIG. 5 is a graph showing an emission intensity waveform of an emission spectrum of a specific wavelength from the etching process to the end thereof.

FIG. 6 is a block diagram showing another example of the configuration of the end point detection device shown in FIG.

FIG. 7 is a diagram showing emission intensity used for calculation in the end point detection device shown in FIG. 6 and XY coordinates of its waveform.

FIG. 8A is a graph showing changes in emission intensity and the slope of the waveform when etching a film having a uniform film thickness. (B) is an XY coordinate that represents the change in the emission intensity of (A) and the slope of the waveform.

FIG. 9 is a cross-sectional view showing a film having a different film thickness depending on a portion.

FIG. 10A is a graph showing changes in the light emission intensity and the slope of the waveform when etching a film having a different film thickness depending on the portion. (B) is an XY coordinate that represents the change in the emission intensity of (A) and the slope of the waveform.

FIG. 11A is a graph showing changes in the emission intensity and the slope of its waveform when etching a film having a uniform overall film thickness. (B) is an XY coordinate that represents the change in the emission intensity of (A) and the slope of the waveform.

FIG. 12 is a cross-sectional view showing a state where a two-layer laminated film is etched at one time based on the method according to the present invention.

FIG. 13A is a graph showing a state in which the emission intensity during etching changes to a convex shape. (B) is an XY coordinate that represents the change in the emission intensity of (A) and the slope of the waveform.
(C) is a graph showing a state in which the emission intensity during etching changes to a convex shape.

[Explanation of symbols]

10 ... Plasma processing device, 11 ... Processing chamber, 12 ... Lower electrode, 13 ... Upper electrode, 14 ... Gas introduction pipe, 15 ... Exhaust pipe, 16 ... High frequency power supply, 17 ... Monitoring window, 21 ... Lens, 21a ... Lens Moving means, 22 ... Photodetector, 30 ...
Endpoint detection device, 31 ... Detection element extractor, 32 ... Average value
Dispersion value calculator, 33 ... calculator, 34 ... comparator, 35 ... judger, 40 ... controller, 41 ... coordinate converter, 42 ... change start judger, 43 ... change end judger, 4
4 ... Origin mover, 50 ... substrate, 51 ... film, 52 ... resist layer, 53a-53c, 63 ... opening, 60 ... semiconductor substrate, 61 ... SiO ₂ film, 62 ... Si ₃ N ₄ film.

Claims (8)

[Claims] 1. A step of sequentially detecting an emission spectrum of an active species having a specific wavelength in the plasma by a photodetector when the object to be processed is treated with plasma, within an initial predetermined time of the processing. Obtaining an average value and a dispersion value of the emission intensity of the emission spectrum, a step of obtaining a calculation value by calculating a difference between the average value and the emission intensity after the lapse of the initial predetermined time, and the calculation value and the dispersion value And determining the time point when the calculated value exceeds a predetermined reference value as the end point of the processing. 2. A step of focusing the light emitted in the plasma when introducing the plasma into the object to be processed and introducing the light into the light detecting means, and the emission spectrum of the active species having a specific wavelength in the plasma. The step of moving the focus position of the focused light so that it can be detected by the photodetector, the step of sequentially detecting the emission spectrum of the active species by the photodetector, and the emission of the emission spectrum within the initial predetermined time of the process. Obtaining a mean value and a dispersion value of the intensity, a step of calculating a difference between the average value and the emission intensity after the lapse of the initial predetermined time to obtain a calculation value, and comparing the calculation value and the dispersion value, A method of detecting an end point, comprising a step of determining a time point when the calculated value exceeds a predetermined reference value as an end point of the processing. 3. A step of sequentially detecting an emission spectrum of an active species having a specific wavelength in the plasma by a photodetector when the object to be processed is treated with plasma, based on information from the emission spectrum. The luminescence intensity and the slope of the waveform of the luminescence intensity by XY coordinates.
And a step of determining a time point at which a newly XY-coordinated point is abruptly separated from the origin of the XY coordinates as an end point of the processing. 4. A step of focusing the light emitted in the plasma when introducing the plasma into the object to be processed and introducing the light into the photodetecting means, the emission spectrum of the active species having a specific wavelength in the plasma. The step of moving the focal position of the focused light so that the light can be detected by the light detection means, the step of sequentially detecting the emission spectrum of the active species by the light detection means, the emission intensity and the information based on the information from the emission spectrum. A step of converting the inclination of the waveform of the emission intensity into XY coordinates,
And a step of determining a time point at which a newly XY-coordinated point is abruptly separated from the origin of the XY coordinates as an end point of the processing. 5. Based on the emission intensity of the emission spectrum obtained by detecting the emission spectrum of the active species having a specific wavelength generated when the object to be processed is treated with plasma, An average value / dispersion value calculation means for obtaining an average value and a dispersion value, a calculation means for obtaining a difference between the average value from the average value / dispersion value calculation means and the emission intensity, a calculation value from the calculation means and the Comparing means for comparing the variance value from the average value / dispersion value computing means, and a determining means for determining the time when the computed value exceeds a predetermined reference value as the end point of the processing by the comparing means, An end point detection device, which detects an end point of the process based on a change in emission intensity of the emission spectrum. 6. The emission intensity of the emission spectrum and the emission intensity obtained by detecting the emission spectrum of an active species having a specific wavelength generated when the object to be treated is treated with plasma by a photodetector. Coordinate conversion means for converting the inclination of the waveform of XY coordinates into XY coordinates, and the distance between the origin of the XY coordinates coordinated by the coordinate conversion means and the point in the XY coordinates newly converted into XY coordinates. Is set as a new origin of XY coordinates, and a first determination means for determining a time point when a value exceeds a predetermined reference value as an end point of the processing, and an end point determined by the first determination means. And an origin moving means for moving the origin to a new origin, and detects the end point of the process based on a change in emission intensity of the emission spectrum. 7. A pair of electrodes arranged in a processing chamber, on which an object to be processed is placed, and a high-frequency electric power being supplied between the electrodes to turn the processing gas into plasma, and the plasma in the processing chamber. A light-collecting means for collecting light emitted therein, a light-detecting means for detecting an emission spectrum from the light collected by the light-collecting means, and a light-emitting intensity based on information from the light-detecting means. An average value / dispersion value calculation means for obtaining an average value and a dispersion value, a calculation means for obtaining a difference between the average value from the average value / dispersion value calculation means and the emission intensity, a calculation value from the calculation means and the Comparing means for comparing the variance value from the average value / dispersion value computing means, and a determining means for determining the time when the computed value exceeds a predetermined reference value as the end point of the processing by the comparing means, Plas on the object The plasma processing apparatus characterized by performing processing using. 8. A pair of electrodes, which are arranged in a processing chamber, a processing target is placed on one side, and a high frequency power is supplied between the electrodes to turn the processing gas into plasma, and the plasma in the processing chamber. A light-collecting means for collecting light emitted therein, a light-detecting means for detecting an emission spectrum from the light collected by the light-collecting means, and a light-emission intensity based on information from the light-detecting means. Coordinate conversion means for converting the slope of the waveform of the emission intensity into XY coordinates, the origin of the XY coordinates coordinated by the coordinate conversion means, and the point in the newly XY coordinates converted into XY coordinates. And a first determination means for determining a time point when the distance between and exceeds a predetermined reference value as an end point of the processing, and an end point determined by the first determination means as a new origin of XY coordinates. , Move the origin to this new origin A plasma processing apparatus comprising: an origin moving unit for moving the object, and performing a process using plasma on the object to be processed.